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Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
Apparatus for calculating a degree of white balance adjustment for a picture Pieces of white balance information indicating color features of a colored picture or picture blocks obtained by partitioning the colored picture are extracted from piece of picture data of the colored picture in an extracting unit. Whether or not a white region exist in the colored picture is judged in a white region judging unit according to the white balance information indicating the color features of the colored picture. When the existence of the white region is judged, a white balance coefficient is calculated in a white balance calculating unit to make the white region white. In contrast, when no existence of any white region is judged, a color distribution axis extending from an original point of a color space to a gravity center of the white balance information indicating the color features of the picture blocks from which pieces of white balance information corresponding to picture blocks of a high chromatic color or a uniform chromaticity are removed is detected in a color distribution axis detecting unit, and the white balance coefficient is calculated to set the color distribution axis to an achromatic color axis of the color space. Therefore, a white balance adjustment adapted to color features of each of colored pictures can be performed.
Attorney, Agent or Firm: What is claimed is: 1. An apparatus for calculating a degree of white balance adjustment for a colored picture, comprising: white balance information extracting means for partitioning a colored picture into a plurality of picture blocks respectively having a uniform size and extracting one or more pieces of white balance information, which each indicates one or more color features of one picture block or one or more color features of the colored picture, from pieces of picture data corresponding to pixels of the colored picture; white region judging and detecting means for judging whether or not a white region having a low chromaticity exists in one of the picture blocks according to the white balance information extracted in the white balance information extracting means and detecting the white region as a basis of white in a white balance adjustment for the colored picture in cases where the white region exists in one of the picture blocks; color distribution axis detecting means for detecting a color distribution axis extending from an original point of a three-dimensional color space to a gravity center of a color distribution of the colored picture according to the white balance information extracted in the white balance information extracting means; white balance coefficient calculating means for calculating a white balance coefficient denoting an amplification gain for colors of pixels of the colored picture according to a color of the white region detected in the white region judging and detecting means in cases where it is judged that the white region exists in one of the picture blocks or according to the color distribution axis detected in the color distribution axis detecting means; and relaxation factor calculating means for calculating a relaxation factor to relax the influence of the color distribution axis detected in the color distribution axis detecting means on the white balance coefficient calculated in the white balance coefficient calculating means, a difference between the white balance coefficient and 1.0 being reduced according to the relaxation factor. 2. An apparatus according to claim 1 in which the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block and a piece of picture maximum-luminance data WPmax indicating a color of a particular maximum-luminance pixel of which a luminance value is the largest among those of maximum-luminance pixels, and it is judged in the white region judging and detecting means that a pixel or a picture block corresponding to the picture maximum-luminance data WPmax is a white region used as a basis of white in a white balance adjustment for the colored picture in cases where a piece of picture data placed farthest from the original point of the three-dimensional color space among the picture data placed in the color distribution of the colored picture agrees with the picture maximum-luminance data WPmax and a luminance value of the picture maximum-luminance data WPmax is higher than a threshold. 3. An apparatus according to claim 1 in which the white balance information extracted in the white balance information extracting means comprises pieces of block average color data AVE respectively indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, a piece of block average color maximum-luminance data AVEmax indicating an average luminance value, an average first color difference value and an average second color difference value of a particular average pixel of which a luminance value is the largest among the average luminance values of the average pixels, and it is judged in the white region judging and detecting means that a pixel or a picture block corresponding to the block average color maximum-luminance data AVEmax is a white region used as a basis of white in a white balance adjustment for the colored picture in cases where a chromaticity of the block average color maximum-luminance data AVEmax is lower than a threshold. 4. An apparatus according to claim 1 in which the color distribution axis detecting means comprises: first-stage color distribution axis calculating means for calculating a first two-dimensional color distribution axis indicating a one-sided condition of a first two-dimensional color distribution obtained by projecting the color distribution of the colored picture onto a first two-dimensional color plane, calculating a second two-dimensional color distribution axis indicating a one-sided condition of a second two-dimensional color distribution obtained by projecting the color distribution of the colored picture onto a second two-dimensional color plane and calculating a first-stage color distribution axis in the three-dimensional color space by synchronizing the first two-dimensional color distribution axis and the second two-dimensional color distribution axis; and second-stage color distribution axis calculating means for selecting pieces of inside white balance information, which exist in a cylindrical space having the first-stage color distribution axis as a central axis in the three-dimensional color space, from the white balance information which are extracted in the white balance information extracting means and indicate the color features of the picture blocks and calculating a second-stage color distribution axis extending from the original point of the three-dimensional color space to a gravity center of the inside white balance information as the color distribution axis detected in the color distribution axis detecting means. 5. An apparatus according to claim 4 in which the first-stage color distribution axis calculating means comprises: first two-dimensional histogram calculating means for calculating a first two-dimensional histogram quantitatively indicating the first two-dimensional color distribution; second two-dimensional histogram calculating means for calculating a second two-dimensional histogram quantitatively indicating the second two-dimensional color distribution; first two-dimensional color distribution axis calculating means for calculating the first two-dimensional color distribution axis according to the first two-dimensional histogram calculated in the first two-dimensional histogram calculating means; second two-dimensional color distribution axis calculating means for calculating the second two-dimensional color distribution axis according to the second two-dimensional histogram calculated in the second two-dimensional histogram calculating means; and three-dimensional color distribution axis generating means for generating the first-stage color distribution axis by synchronizing the first two-dimensional color distribution axis calculated in the first two-dimensional color distribution axis calculating means and the second two-dimensional color distribution axis calculated in the second two-dimensional color distribution axis calculating means. 6. An apparatus according to claim 5, the first-stage color distribution axis calculating means further comprising: angle storing means for storing a plurality of first angles respectively corresponding to a first referential position indicated by two types of variables of the first two-dimensional histogram and storing a plurality of second angles respectively corresponding to a second referential position indicated by two types of variables of the second two-dimensional histogram, each first angle being defined as an angle between a line connecting one first referential position and an original point of the first two-dimensional color plane and an co-ordinate axis of the first two-dimensional color plane, and each second angle being defined as an angle between a line connecting one second referential position and an original point of the second two-dimensional color plane and an co-ordinate axis of the second two-dimensional color plane; and weighting factor storing means for storing a plurality of weighting factors corresponding to the first and second angles stored in the angle storing means, a value of each weighting factor being decreased as the first or second angle becomes far from an angle of 45 degrees, wherein a plurality of first angles corresponding to first positions indicated by a plurality of sets of variables of the first two-dimensional histogram are weighted with weighting factors corresponding to the first angles in the first two-dimensional color distribution axis calculating means to generate a plurality of first weighted angles, an angle between the first two-dimensional color distribution axis and the co-ordinate axis of the first two-dimensional color plane is set to a first weighted average angle determined by averaging the first weighted angles in the first two-dimensional color distribution axis calculating means, a plurality of second angles corresponding to second positions indicated by a plurality of sets of variables of the second two-dimensional histogram are weighted with weighting factors corresponding to the second angles in the second two-dimensional color distribution axis calculating means to generate a plurality of second weighted angles, and an angle between the second two-dimensional color distribution axis and the co-ordinate axis of the second two-dimensional color plane is set to a second weighted average angle determined by averaging the first weighted angles in the second two-dimensional color distribution axis calculating means. 7. An apparatus according to claim 4 in which the first-stage color distribution axis calculating means comprises: removing block detecting means for detecting a picture block, which is partitioned in the white balance information extracting means and has a uniform chromatic color, as a removing picture block; first two-dimensional histogram calculating means for calculating a first two-dimensional histogram quantitatively indicating a first two-dimensional processed color distribution obtained by projecting a processed color distribution of the picture blocks of the colored picture except for the removing picture block detected in the removing block detecting means onto the first two-dimensional color plane; second two-dimensional histogram calculating means for calculating a second two-dimensional histogram quantitatively indicating a second two-dimensional processed color distribution obtained by projecting the processed color distribution onto the second two-dimensional color plane; first two-dimensional color distribution axis calculating means for calculating the first two-dimensional color distribution axis according to the first two-dimensional histogram calculated in the first two-dimensional histogram calculating means; second two-dimensional color distribution axis calculating means for calculating the second two-dimensional color distribution axis according to the second two-dimensional histogram calculated in the second two-dimensional histogram calculating means; and three-dimensional color distribution axis generating means for generating the first-stage color distribution axis by synchronizing the first two-dimensional color distribution axis calculated in the first two-dimensional color distribution axis calculating means and the second two-dimensional color distribution axis calculated in the second two-dimensional color distribution axis calculating means. 8. An apparatus according to claim 7 in which the white balance information extracted in the white balance information extracting means comprises a piece of block average color data AVE indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in a particular picture block and a piece of block minimum-luminance data BP indicating a color of a minimum-luminance pixel of which a luminance value is the smallest among those of pixels in the same particular picture block, and the particular picture block is detected as the removing picture block in the removing block detecting means in cases where a difference between the average luminance value of the block average color data AVE and the luminance value of the block minimum-luminance data BP is lower than a first threshold, a chromaticity of the block average color data AVE and a chromaticity of the block minimum-luminance data BP are respectively equal to or higher than a second threshold, and a difference between a hue value of the block average color data AVE and a hue value of the block minimum-luminance data BP is lower than a third threshold. 9. An apparatus according to claim 7, the first-stage color distribution axis calculating means further comprising: angle storing means for storing a plurality of first angles respectively corresponding to a first referential position indicated by two types of variables of the first two-dimensional histogram and storing a plurality of second angles respectively corresponding to a second referential position indicated by two types of variables of the second two-dimensional histogram, each first angle being defined as an angle between a line connecting one first referential position and an original point of the first two-dimensional color plane and an co-ordinate axis of the first two-dimensional color plane, and each second angle being defined as an angle between a line connecting one second referential position and an original point of the second two-dimensional color plane and an co-ordinate axis of the second two-dimensional color plane; and weighting factor storing means for storing a plurality of weighting factors corresponding to the first and second angles stored in the angle storing means, a value of each weighting factor being decreased as the first or second angle becomes far from an angle of 45 degrees, wherein a plurality of first angles corresponding to first positions indicated by a plurality of sets of variables of the first two-dimensional histogram are weighted with weighting factors corresponding to the first angles in the first two-dimensional color distribution axis calculating means to generate a plurality of first weighted angles, an angle between the first two-dimensional color distribution axis and the co-ordinate axis of the first two-dimensional color plane is set to a first weighted average angle determined by averaging the first weighted angles in the first two-dimensional color distribution axis calculating means, a plurality of second angles corresponding to second positions indicated by a plurality of sets of variables of the second two-dimensional histogram are weighted with weighting factors corresponding to the second angles in the second two-dimensional color distribution axis calculating means to generate a plurality of second weighted angles, and an angle between the second two-dimensional color distribution axis and the co-ordinate axis of the second two-dimensional color plane is set to a second weighted average angle determined by averaging the first weighted angles in the second two-dimensional color distribution axis calculating means. 10. An apparatus according to claim 4 in which the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block and pieces of block average color data AVE respectively indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in one picture block, and the second-stage color distribution axis calculating means comprises: WP data gravity center calculating means for calculating a WP gravity center of pieces of inside block maximum-luminance data WP which are selected from the block maximum-luminance data WP extracted in the white balance information extracting means and are placed in the cylindrical region of the three-dimensional color space; AVE data gravity center calculating means for calculating a AVE gravity center of pieces of inside block minimum-luminance data AVE which are selected from the block minimum-luminance data AVE extracted in the white balance information extracting means and are placed in the cylindrical region of the three-dimensional color space; and average value calculating means for calculating an average position of the WP gravity center calculated in the WP data gravity center calculating means and AVE gravity center calculated in the AVE data gravity center calculating means, the second-stage color distribution axis being defined as a line segment extending from the original point of the three-dimensional color space to the average position. 11. An apparatus according to claim 1 in which the relaxation factor calculating means comprises: a plurality of relaxation factor calculating units for respectively calculating a relaxation factor of which a value is set according to a chromaticity value of a piece of white balance information which indicates color features of the colored picture and is extracted in the white balance information extracting means; and a maximum value selecting unit for selecting one relaxation factor having a maximum value from among the relaxation factors calculated in the relaxation factor calculating units as the relaxation factor calculated in the relaxation factor calculating means. 12. An apparatus according to claim 1 in which the relaxation factor calculating means comprises: a hue histogram generating unit for preparing six hue regions partitioned by red, yellow, green, cyan, blue and magenta in that order and arranged in a cyclic form and generating a hue histogram having six hue variables which each designate the number of pieces of white balance information which are extracted in the white balance information extracting means for each picture block and are placed in the same hue region; a histogram type recognizing unit for recognizing whether or not a color distribution of the colored picture is one-sided according to a distribution condition of the hue variables of the hue histogram generated in the hue histogram generating unit; a plurality of relaxation factor calculating units for respectively calculating a relaxation factor of which a value is set according to the recognition of the color distribution of the colored picture performed in the histogram type recognizing unit and a chromaticity value of a piece of white balance information which indicates color features of the colored picture and is extracted in the white balance information extracting means; and a maximum value selecting unit for selecting one relaxation factor having a maximum value from among the relaxation factors calculated in the relaxation factor calculating units as the relaxation factor calculated in the relaxation factor calculating means. 13. An apparatus according to claim 12 in which it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is one-sided in cases where the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables corresponding to two hue regions adjacent to each other or the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables having a complementary color relationship, and a value of the relaxation factor calculated in each of the relaxation factor calculating units in cases where it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is one-sided is higher than that in cases where it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is not one-sided. 14. An apparatus according to claim 12 in which a variable threshold is determined in the histogram type recognizing unit according to the number of picture blocks generated in the white balance information extracting means and the number of hue regions corresponding to hue variables of the hue histogram which each are not zero, and it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is one-sided in cases where the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables which are higher than the variable threshold and correspond to two hue regions adjacent to each other or the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables which are higher than the variable threshold and have a complementary color relationship. 15. An apparatus according to claim 12 in which the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block, pieces of block average color data AVE respectively indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in one picture block, a piece of block maximum-luminance average color data WPave indicating an average luminance value, an average first color difference value and an average second color difference value among luminance values, first color difference values and second color difference values of the maximum-luminance pixels, a piece of block average color maximum-luminance data AVEmax indicating an average luminance value, an average first color difference value and an average second color difference value of a particular average pixel of which a luminance value is the largest among the average luminance values of the average pixels and a piece of picture average color data AVEave indicating an average luminance value, an average first color difference value and an average second color difference value among the luminance values, the first color difference values and the second color difference values indicated by the pieces of block average color data AVE, each of the block average color data AVE extracted in the white balance information corresponds to one of the hue regions, each of the hue variables of the hue histogram generated in the hue histogram generating unit designates the number of pieces of block average color data AVE which are extracted in the white balance information extracting means and corresponds to the same hue region, a first relaxation factor of which a value is monotonically increased as a chromaticity value of the block maximum-luminance average color data WPave extracted in the white balance information extracting means is increased is calculated in a first relaxation factor calculating unit of the relaxation factor calculating units, a second relaxation factor of which a value is monotonically increased as a chromaticity value of the block average color maximum-luminance data AVEmax extracted in the white balance information extracting means is increased is calculated in a second relaxation factor calculating unit of the relaxation factor calculating units, a third relaxation factor of which a value is monotonically increased as a chromaticity value of the picture average color data AVEave extracted in the white balance information extracting means is increased is calculated in a third relaxation factor calculating unit of the relaxation factor calculating units, and a relaxation factor having a maximum value among those of the first, second and third relaxation factors is selected in the maximum value selecting unit. 16. An apparatus according to claim 1 in which the white balance coefficient functioning as the amplification gain for the colors of the colored picture is calculated in the white balance-coefficient calculating means according to the color distribution axis detected in the color distribution axis detecting means to place a reproduced gravity center of reproduced colors of the colored picture, which are obtained by amplifying the colors of the colored picture by the white balance coefficient, on an achromatic color axis of the three-dimensional color axis, and the white balance coefficient is decreased in the white balance coefficient calculating means by compressing a variation value of the white balance coefficient from 1.0 according to the relaxation factor calculated in the relaxation factor calculating means. 17. An apparatus according to claim 1 in which the white balance coefficient functioning as the amplification gain for the colors of the colored picture is calculated in the white balance coefficient calculating means according to the color distribution axis detected in the color distribution axis detecting means to place a reproduced gravity center of reproduced colors of the colored picture, which are obtained by amplifying the colors of the colored picture by the white balance coefficient, on an achromatic color axis of the three-dimensional color axis, the white balance coefficient is decreased in the white balance coefficient calculating means by compressing a variation value of the white balance coefficient from one according to the relaxation factor calculated in the relaxation factor calculating means, and the white balance coefficient is again decreased in an allowable range in the white balance coefficient calculating means by compressing a variation value of the white balance coefficient from one in cases where the white balance coefficient decreased according to the relaxation factor is out of the allowable range. 18. An apparatus according to claim 1, further comprising: white balance adjustment mode setting means for setting a first white balance adjustment mode in cases where a white region having a sufficiently low chromaticity is detected in the white region judging and detecting means, setting a second white balance adjustment mode in cases where any white region having a low chromaticity is not detected in the white region judging and detecting means and setting a third white balance adjustment mode in cases where a white region having a low chromaticity near to white is detected in the white region judging and detecting means, wherein the white balance coefficient is calculated in the white balance coefficient calculating means according to a color of the white region in case of the first white balance adjustment mode, the white balance coefficient is calculated in the white balance coefficient calculating means according to the color distribution axis in case of the second white balance adjustment mode, and the white balance coefficient is calculated in the white balance coefficient calculating means according to a color of the white region and the gravity center indicated by the color distribution axis in case of the third white balance adjustment mode. 19. An apparatus according to claim 18 in which the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block and a piece of picture maximum-luminance data WPmax(WXr, WXg, WXb) indicating three primary colors of a particular maximum-luminance pixel of which a luminance value is the largest among those of maximum-luminance pixels, first, second and third components WBkr, WBkg and WBkb of the white balance coefficient for three primary colors R, G and B of the colored picture are calculated in the white balance coefficient calculating means according to a first equation in cases where the first white balance adjustment mode is set in the white balance adjustment mode setting means, the components WBkr, WBkg and WBkb of the white balance coefficient are calculated in the white balance coefficient calculating means by using a vector (WBr, WBg, WBb) of the color distribution axis detected in the color distribution axis detecting means according to a second equation in cases where the second white balance adjustment mode is set in the white balance adjustment mode setting means, and the components WBkr, WBkg and WBkb of the white balance coefficient are calculated in the white balance coefficient calculating means by using the vector (WBr, WBg, WBb) of the color distribution axis and the picture maximum-luminance data WPmax(WXr, WXg, WXb) according to a third equation in cases where the third white balance adjustment mode is set in the white balance adjustment mode setting means. 20. An apparatus according to claim 1, further comprising: white balance adjustment judging means for judging whether or not a white balance of the colored picture is sufficiently kept and judging whether or not a major portion of the colored picture is occupied by an object having a chromatic color according to the white balance information extracted in the white balance information extracting means, wherein the detection of the white region performed in the white region judging and detecting means and the detection of the color distribution axis performed in the color distribution axis detecting means are stopped in cases where it is judged that a white balance of the colored picture is sufficiently kept or a major portion of the colored picture is occupied by an object having a chromatic color. 21. An apparatus according to claim 20 in which the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block, pieces of block average color data AVE respectively indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in one picture block, a piece of picture maximum-luminance data WPmax indicating a color of a particular maximum-luminance pixel of which a luminance value is the largest among those of maximum-luminance pixels, a piece of block maximum-luminance average color data WPave indicating an average luminance value, an average first color difference value and an average second color difference value among luminance values, first color difference values and second color difference values of the maximum-luminance pixels, a piece of block average color maximum-luminance data AVEmax indicating an average luminance value, an average first color difference value and an average second color difference value of a particular average pixel of which a luminance value is the largest among the average luminance values of the average pixels, a piece of picture average color data AVEave indicating an average luminance value, an average first color difference value and an average second color difference value among the luminance values, the first color difference values and the second color difference values indicated by the pieces of block average color data AVE, a piece of squared chromaticity data WXsqc defined as a sum of a squared first color difference value of the picture maximum-luminance data WPmax and a squared second color difference value of the picture maximum-luminance data WPmax, a piece of squared chromaticity data WAsqc defined as a sum of a squared average first color difference value of the block maximum-luminance average color data WPave and a squared average second color difference value of the block maximum-luminance average color data WPave, a piece of squared chromaticity data AXsqc defined as a sum of a squared average first color difference value of the block average color maximum-luminance data AVEmax and a squared average second color difference value of the block average color maximum-luminance data AVEmax and a piece of squared chromaticity data AAsqc defined as a sum of a squared average first color difference value of the picture average color data AVEave and a squared average second color difference value of the picture average color data AVEave, and it is judged in the white balance adjustment judging means that a major portion of the colored picture is occupied by an object having a chromatic color in cases where the squared chromaticity data WAsqc is equal to or higher than a first threshold, the squared chromaticity data AXsqc is equal to or higher than a second threshold and the squared chromaticity data AAsqc is equal to or higher than a third threshold or it is judged in the white balance adjustment judging means that a white balance of the colored picture is sufficiently kept in cases where the squared chromaticity data WXsqc is equal to or lower than a fourth threshold and the squared chromaticity data WAsqc is equal to or lower than a fifth threshold. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an apparatus for calculating a degree of white balance adjustment for a picture, and more particularly to an apparatus for calculating a degree of white balance adjustment for a picture which is used for a color image outputting apparatus such as a color video printer, a color copy machine or the like and is appropriate to perform a hard-copy of a picture. 2. Description of the Related Art In many types of video cameras and video movies, an auto white balance adjustment function is provided, and the white balance adjustment is performed on the assumption that an integrated value (or an average value) of color difference signals for a picture in which an appropriate white balance is kept becomes zero. However, in cases where a chromatic-colored object is pictured to occupy a wide region of the picture, the assumption is not necessarily correct. Therefore, when the auto white balance adjustment is performed, a picture quality often deteriorates. For example, a picture adjusted in auto white balance is faded. 2.1. Previously Proposed Art To solve this problem, many auto white balance adjusting methods in which many types of improvement are performed are developed and disclosed. For example, in an adjusting method disclosed in the Published Unexamined Japanese Patent Application No. H3-274884 (274884/1991), a plurality of color difference signals of pixels which have colors near to white and are placed in a rectangular region along a black-body radiation curve in a color space are integrated to perform the white balance adjustment. Also, in an adjusting method disclosed in the Published Unexamined Japanese Patent Application No. H3-250992 (250992/1991), a photographed picture is partitioned into 8.times.8 regions, an integrated value of color difference signals for each of the regions is estimated, and the adverse influence of a high chromatic-colored object pictured in a region on a white balance adjustment for all regions of the photographed picture is reduced. However, these types of improvement are not sufficient to perform the auto white balance adjustment with high accuracy without any deterioration of picture quality. Also, a picture quality of an image printed by a video printer is influenced by the quality of picture signals input to a television, a video tape recorder, a laser disk, a video movie or the like. Therefore, it is required to consider that the picture signals in which any white balance adjustment is not performed because of a manual photographing are reproduced by the video printer. Even though the auto white balance adjustment is performed for the picture signals in a photographing apparatus, the picture signals in which the auto white balance adjustment is not sufficient or is erroneously performed are reproduced by the video printer. Therefore, the auto white balance adjustment sufficiently performed with high accuracy is required of a color image outputting apparatus. 2.2. Problems to be Solved by the Invention A conventional video printer having an auto white balance function is disclosed in the Published Unexamined Japanese Patent Application No. H2-298194 (298194/1990). In this Application, a degree of white balance adjustment is calculated on the basis of an integrated value of color difference signals, in the same manner as that in the white balance adjusting method for the video camera. However, there is a problem that the white valance adjustment is erroneously performed because of the existence of a high chromatic object in the same manner as the white balance adjustment in the video camera. Also, in the Published Unexamined Japanese Patent Application No. H4-323994 (323994/1992), a chromaticity threshold is used to remove pixels relating to a high chromaticity and to select pixels relating to low chromaticity for the purpose of avoiding adverse influence of the high chromaticity, and the white balance adjustment is performed by using information relating to the low chromaticity. However, in cases where the white balance is not kept in a picture, an achromatic color used as a basis of chromatic colors cannot be defined, and chromaticity cannot be determined with high reliability. That is, an appropriate white balance adjustment cannot be necessarily performed. Therefore, in cases where the white balance adjustment is performed on the basis of an integrated value of color difference signals, it is important how the adverse influence of a high chromaticity region in a picture is removed to calculate a degree of white balance adjustment without any erroneous adjustment. Also, in cases where a white region slightly colored exists in a picture, it is preferred that the white balance adjustment be not performed on the basis of an integrated value of color difference signals but the white balance adjustment be performed on the basis of the white region. Accordingly, it is preferred that the white balance adjustment based on an integrated value of color difference signals or the white balance adjustment based on a white region detected be selected by considering features of a color distribution of a picture. SUMMARY OF THE INVENTION An object of the present invention is to provide, with due consideration to the drawbacks of such a conventional apparatus for calculating a degree of white balance adjustment, an apparatus for calculating a degree of white balance adjustment for a picture in which a white balance adjustment appropriate to a colored picture reproduced by a colored picture outputting apparatus such as a video printer is selectively performed without any erroneous adjustment and the adverse influence of a high chromaticity region of the colored picture is hardly received. The object is achieved by the provision of an apparatus for calculating a degree of white balance adjustment for a picture, comprising: white balance information extracting means for partitioning a colored picture into a plurality of picture blocks respectively having an uniform size and extracting one or more pieces of white balance information, which each indicate one or more color features of one picture block or one or more color features of the colored picture, from pieces of picture data corresponding to pixels of the colored picture; white region judging and detecting means for judging whether or not a white region having a low chromaticity exists in one of the picture blocks according to the white balance information extracted in the white balance information extracting means and detecting the white region as a basis of white in a white balance adjustment for the colored picture in cases where the white region exists in one of the picture blocks; color distribution axis detecting means for detecting a color distribution axis extending from an original point of a three-dimensional color space to a gravity center of a color distribution of the colored picture according to the white balance information extracted in the white balance information extracting means; white balance coefficient calculating means for calculating a white balance coefficient denoting an amplification gain for colors of pixels of the colored picture according to a color of the white region detected in the white region judging and detecting means in cases where it is judged that the white region exists in one of the picture blocks or according to the color distribution axis detected in the color distribution axis detecting means, the white balance coefficient varying around 1.0; and relaxation factor calculating means for calculating a relaxation factor to relax the influence of the color distribution axis detected in the color distribution axis detecting means on the white balance coefficient calculated in the white balance coefficient calculating means, a difference between the white balance coefficient and 1.0 being reduced according to the relaxation factor. In the above configuration, pieces of white balance information indicating color features of each picture block or color features of a colored picture are extracted from pieces of picture data in the white balance information extracting means. Thereafter, it is judged in the white region judging and detecting means whether or not a white region having a low chromaticity exists in one of the picture blocks according to the white balance information. In cases where the white region exists in one picture block, a white balance coefficient is calculated in the white balance coefficient calculating means according to a color of the white region. The white balance coefficient calculated functions as an amplification gain for pixels of the colored picture. Therefore, the white balance adjustment adapted to color features of the colored picture can be performed. Also, a color distribution axis is detected in the color distribution axis detecting means according to the white balance information. The color distribution axis is defined as a line segment extending from an original point (or a black point) of a three-dimensional color space to a gravity center of a color distribution of the colored picture. Thereafter, a white balance coefficient is calculated in the white balance coefficient calculating means according to a color at the gravity center of the color distribution of the colored picture. Thereafter, a difference between the white balance coefficient calculated and 1.0 is reduced by a relaxation factor calculated in the relaxation factor calculating means. Therefore, because the influence of the color distribution axis on the white balance coefficient is reduced by the relaxation factor, it can be prevented that a color of an object placed in a major portion of the colored picture changes to its complementary color, and it can be prevented that a viewer feels strange for colors of a colored picture. Accordingly, a white balance adjustment appropriate to a colored picture reproduced by a colored picture outputting apparatus such as a video printer can be selectively performed without any erroneous adjustment, and the adverse influence of a high chromaticity region of the colored picture is hardly received. It is preferred that the white balance information extracted in the white balance information extracting means comprise pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block and a piece of picture maximum-luminance data WPmax indicating a color of a particular maximum-luminance pixel of which a luminance value is the largest among those of maximum-luminance pixels, and it be judged in the white region judging and detecting means that a pixel or a picture block corresponding to the picture maximum-luminance data WPmax is a white region used as a basis of white in a white balance adjustment for the colored picture in cases where a piece of picture data placed farthest from the original point of the three-dimensional color space among the picture data placed in the color distribution of the colored picture agrees with the picture maximum-luminance data WPmax and a luminance value of the picture maximum-luminance data WPmax is higher than a threshold. In the above configuration, in cases where a major portion of a colored picture is not occupied by any chromatic colored object having a high chromaticity, a color distribution of pieces of picture data of the colored picture is formed in a spindle shape which extends in a luminance direction in a three-dimensional color space. Also, in cases where a white balance is kept in the colored picture, a major-component axis of the color distribution for the colored picture almost agrees with an achromatic color axis of the color space. In this case, a piece of picture data placed at a top portion of the color distribution in a high luminance direction is farthest from the original point of the color space and agrees with the picture maximum-luminance data WPmax. Therefore, the picture maximum-luminance data WPmax can be used as a piece of reference data for the white balance adjustment. In addition, in cases where a luminance of the picture maximum-luminance data WPmax is sufficiently high, a probability that a color designated by the picture maximum-luminance data WPmax is white is heightened. Also, it is preferred that the color distribution axis detecting means comprise first-stage color distribution axis calculating means for calculating a first two-dimensional color distribution axis indicating a one-sided condition of a first two-dimensional color distribution obtained by projecting the color distribution of the colored picture onto a first two-dimensional color plane, calculating a second two-dimensional color distribution axis indicating a one-sided condition of a second two-dimensional color distribution obtained by projecting the color distribution of the colored picture onto a second two-dimensional color plane and calculating a first-stage color distribution axis in the three-dimensional color space by synchronizing the first two-dimensional color distribution axis and the second two-dimensional color distribution axis; and second-stage color distribution axis calculating means for selecting pieces of inside white balance information, which exist in a cylindrical space having the first-stage color distribution axis as a central axis in the three-dimensional color space, from the white balance information which are extracted in the white balance information extracting means and indicate the color features of the picture blocks and calculating a second-stage color distribution axis extending from the original point of the three-dimensional color space to a gravity center of the inside white balance information as the color distribution axis detected in the color distribution axis detecting means. In the above configuration, a first-stage color distribution axis roughly indicating a one-sided condition of the color distribution of the colored picture is calculated in the first-stage color distribution axis calculating means. Thereafter, a second-stage color distribution axis indicating a one-sided condition of the color distribution of the colored picture is calculated on condition that pieces of white balance information placed out of the cylindrical space are not considered to prevent the influence of a high chromatic colored object on the calculation of the second-stage color distribution axis. Therefore, an adverse influence of a high chromatic colored object on the white balance adjustment can be removed. In addition, it is preferred that the first-stage color distribution axis calculating means comprise: removing block detecting means for detecting a picture block, which is partitioned in the white balance information extracting means and has a uniform chromatic color, as a removing picture block; first two-dimensional histogram calculating means for calculating a first two-dimensional histogram quantitatively indicating a first two-dimensional processed color distribution obtained by projecting a processed color distribution of the picture blocks of the colored picture except for the removing picture block detected in the removing block detecting means onto the first two-dimensional color plane; second two-dimensional histogram calculating means for calculating a second two-dimensional histogram quantitatively indicating a second two-dimensional processed color distribution obtained by projecting the processed color distribution onto the second two-dimensional color plane; first two-dimensional color distribution axis calculating means for calculating the first two-dimensional color distribution axis according to the first two-dimensional histogram calculated in the first two-dimensional histogram calculating means; second two-dimensional color distribution axis calculating means for calculating the second two-dimensional color distribution axis according to the second two-dimensional histogram calculated in the second two-dimensional histogram calculating means; and three-dimensional color distribution axis generating means for generating the first-stage color distribution axis by synchronizing the first two-dimensional color distribution axis calculated in the first two-dimensional color distribution axis calculating means and the second two-dimensional color distribution axis calculated in the second two-dimensional color distribution axis calculating means, the white balance information extracted in the white balance information extracting means comprise a piece of block average color data AVE indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in a particular picture block and a piece of block minimum-luminance data BP indicating a color of a minimum-luminance pixel of which a luminance value is the smallest among those of pixels in the same particular picture block, and the particular picture block be detected as the removing picture block in the removing block detecting means in cases where a difference between the average luminance value of the block average color data AVE and the luminance value of the block minimum-luminance data BP is lower than a first threshold, a chromaticity of the block average color data AVE and a chromaticity of the block minimum-luminance data BP are respectively equal to or higher than a second threshold, and a difference between a hue value of the block average color data AVE and a hue value of the block minimum-luminance data BP is lower than a third threshold. In the above configuration, in cases where the color designated by the block average color data AVE similar to the color designated by the block minimum-luminance data BP, the particular picture block corresponding to the data AVE and BP is detected as the removing picture block in the removing block detecting means, and the first-stage color distribution axis is generated in the three-dimensional color distribution axis generating means without using the data AVE and BP corresponding to the particular picture block. Therefore, an adverse influence of a picture block occupied by a uniform chromatic color on the calculation of the first-stage color distribution axis can be removed. Also, it is preferred that the relaxation factor calculating means comprise: a hue histogram generating unit for preparing six hue regions partitioned by red, yellow, green, cyan, blue and magenta in that order and arranged in a cyclic form and generating a hue histogram having six hue variables which each designate the number of pieces of white balance information which are extracted in the white balance information extracting means for each picture block and are placed in the same hue region; a histogram type recognizing unit for recognizing whether or not a color distribution of the colored picture is one-sided according to a distribution condition of the hue variables of the hue histogram generated in the hue histogram generating unit; a plurality of relaxation factor calculating units for respectively calculating a relaxation factor of which a value is set according to the recognition of the color distribution of the colored picture performed in the histogram type recognizing unit and a chromaticity value of a piece of white balance information which indicates color features of the colored picture and is extracted in the white balance information extracting means; and a maximum value selecting unit for selecting one relaxation factor having a maximum value from among the relaxation factors calculated in the relaxation factor calculating units as the relaxation factor calculated in the relaxation factor calculating means, it be recognized in the histogram type recognizing unit that the color distribution of the colored picture is one-sided in cases where the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables corresponding to two hue regions adjacent to each other or the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables having a complementary color relationship, and a value of the relaxation factor calculated in each of the relaxation factor calculating units in cases where it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is one-sided be higher than that in cases where it is recognized in the histogram type recognizing unit that the color distribution of the colored picture is not one-sided. In the above configuration, in cases where the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables corresponding to two hue regions adjacent to each other, colors of a plurality of pixels of the colored picture are locally distributed around a particular color corresponding to the hue regions adjacent to each other, the color distribution axis detected in the color distribution axis detecting means is greatly inclined toward the particular color, and colors of many pixels undesirably change toward a complementary color as a result of the white balance adjustment. Therefore, a relaxation factor having a high value is set to decrease a degree of the white balance adjustment. Also, in cases where the distribution condition of the hue variables of the hue histogram is one-sided to two hue variables having a complementary color relationship, it is easy that the color distribution axis is erroneously detected in the color distribution axis detecting means. Therefore, a relaxation factor having a high value is set to decrease a degree of the white balance adjustment. Accordingly, it can be prevented that a color of an object placed in a major portion of the colored picture changes to its complementary color, and it can be prevented that a viewer feels strange for colors of a colored picture. Also, it is preferred that the apparatus further comprise: white balance adjustment judging means for judging whether or not a white balance of the colored picture is sufficiently kept and judging whether or not a major portion of the colored picture is occupied by an object having a chromatic color according to the white balance information extracted in the white balance information extracting means, wherein the detection of the white region performed in the white region judging and detecting means and the detection of the color distribution axis performed in the color distribution axis detecting means are stopped in cases where it is judged that a white balance of the colored picture is sufficiently kept or a major portion of the colored picture is occupied by an object having a chromatic color, the white balance information extracted in the white balance information extracting means comprises pieces of block maximum-luminance data WP respectively indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block, pieces of block average color data AVE respectively indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in one picture block, a piece of picture maximum-luminance data WPmax indicating a color of a particular maximum-luminance pixel of which a luminance value is the largest among those of maximum-luminance pixels, a piece of block maximum-luminance average color data WPave indicating an average luminance value, an average first color difference value and an average second color difference value among luminance values, first color difference values and second color difference values of the maximum-luminance pixels, a piece of block average color maximum-luminance data AVEmax indicating an average luminance value, an average first color difference value and an average second color difference value of a particular average pixel of which a luminance value is the largest among the average luminance values of the average pixels, a piece of picture average color data AVEave indicating an average luminance value, an average first color difference value and an average second color difference value among the luminance values, the first color difference values and the second color difference values indicated by the pieces of block average color data AVE, a piece of squared chromaticity data WXsqc defined as a sum of a squared first color difference value of the picture maximum-luminance data WPmax and a squared second color difference value of the picture maximum-luminance data WPmax, a piece of squared chromaticity data WAsqc defined as a sum of a squared average first color difference value of the block maximum-luminance average color data WPave and a squared average second color difference value of the block maximum-luminance average color data WPave, a piece of squared chromaticity data AXsqc defined as a sum of a squared average first color difference value of the block average color maximum-luminance data AVEmax and a squared average second color difference value of the block average color maximum-luminance data AVEmax and a piece of squared chromaticity data AAsqc defined as a sum of a squared average first color difference value of the picture average color data AVEave and a squared average second color difference value of the picture average color data AVEave, and it is judged in the white balance adjustment judging means that a major portion of the colored picture is occupied by an object having a chromatic color in cases where the squared chromaticity data WAsqc is equal to or higher than a first threshold, the squared chromaticity data AXsqc is equal to or higher than a second threshold and the squared chromaticity data AAsqc is equal to or higher than a third threshold or it is judged in the white balance adjustment judging means that a white balance of the colored picture is sufficiently kept in cases where the squared chromaticity data WXsqc is equal to or lower than a fourth threshold and the squared chromaticity data WAsqc is equal to or lower than a fifth threshold. In the above configuration, in cases where it is judged that a major portion of the colored picture is occupied by an object having a chromatic color, an average chromaticity of the colored picture becomes extremely high, and a probability that the white balance adjustment is erroneously performed is high. Therefore, the detection of the white region performed in the white region judging and detecting means and the detection of the color distribution axis performed in the color distribution axis detecting means are stopped by the white balance adjustment judging means. Also, in cases where it is judged that a white balance of the colored picture is sufficiently kept, colors of the colored picture is locally distributed in a color region close to an achromatic color axis (or a line segment extending from black to white) of the color space. Therefore, any white balance adjustment is not required, and the detection of the white region performed in the white region judging and detecting means and the detection of the color distribution axis performed in the color distribution axis detecting means are stopped by the white balance adjustment judging means. BRIEF DESCRIPTION OF THE DRAWINGS The objects, features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a block diagram of an apparatus for adjusting white balance in a colored picture according to an embodiment of the present invention; FIG. 2 shows a conceptual view of a plurality of picture blocks obtained by partitioning the colored picture of which the white balance is adjusted in the apparatus shown in FIG. 1; FIG. 3 is a flow chart showing the procedure performed in an apparatus shown in FIG. 1 in which a degree of white balance adjustment for the colored picture is calculated; FIG. 4 is a block diagram of a color distribution axis detecting unit shown in FIG. 1; FIG. 5 is a flow chart showing the operation performed in a first-stage color distribution axis detecting unit shown in FIG. 4; FIG. 6 is a conceptual view of six simplified hue regions used to calculate GR and GB two-dimensional histograms obtained in the first-stage color distribution axis detecting unit shown in FIG. 4; FIG. 7 is a flow chart showing the procedure for determining a simplified hue region number corresponding to a piece of white balance information extracted in a white balance information extracting unit shown in FIG. 1 according to color features of the white balance information; FIG. 8 is a conceptual view of a plurality of GR angles stored in an angle table ROM of the first-stage color distribution axis detecting unit shown in FIG. 4; FIG. 9 is a flow chart showing the operation performed in a second-stage color distribution axis detecting unit shown in FIG. 4; FIG. 10 is a block diagram of a relaxation factor calculating unit shown in FIG. 1; FIG. 11 is a flow chart showing the operation performed in the relaxation factor calculating unit shown in FIG. 10; FIG. 12 shows an example of a color distribution of picture blocks of a colored picture of which hue is one-sided to green; FIG. 13 shows an example of a color distribution of picture blocks of a colored picture in which a pair of colors having a complementary color relationship exist; and FIG. 14 shows a relationship between a normalized squared chromaticity value and a relaxation factor. DETAILED DESCRIPTION OF THE EMBODIMENTS Preferred embodiments of an apparatus for calculating a degree of white balance adjustment for a picture according to the present invention are described with reference to drawings. FIG. 1 is a block diagram of an apparatus for adjusting white balance in a picture according to an embodiment of the present invention. As shown in FIG. 1, an apparatus 11 for adjusting white balance in a picture comprises a picture memory 12 for storing a plurality of picture signals of a colored picture as pieces of picture data respectively relating to a pixel of the colored picture, an apparatus 13 for calculating a degree of white balance adjustment for the colored picture by analyzing color features of the colored picture according to the picture data, and a white balance adjusting unit 14 for performing a white valance adjustment for the colored picture according to the degree of white balance adjustment calculated in the apparatus 13. The apparatus 13 for calculating a degree of white balance adjustment for the colored picture comprises: a white balance information extracting unit 15 for partitioning the colored picture into a plurality of picture blocks having the same size and extracting pieces of white balance information required to adjust a white balance for the colored picture, the white balance information being classified into pieces of block color information which indicate color features of each picture block and pieces of picture color information which indicate color features of the entire colored picture; a white balance information storing unit 16 for storing the white balance information extracted in the extracting unit 15; and a white balance adjustment judging unit 17 for judging whether or not a white balance adjustment for the colored picture is required, according to the picture color information of the white balance information stored in the storing unit 16. In cases where it is judged in the judging unit 17 that any white balance adjustment is not required or the white balance adjustment is difficult, the calculation of a degree of white balance adjustment in the apparatus 13 is stopped. The apparatus 13 further comprises: a white region judging and detecting unit 18 for judging whether or not a white region to be used as a basis of the white balance adjustment exists in one of the picture blocks according to the white balance information stored in the storing unit 16 and detecting the white region in cases where the white region exists in one of the picture blocks; a white balance adjustment mode setting unit 19 for setting a white balance adjustment mode according to the judgement of the judging and detecting unit 18 in cases where it is judged in the judging unit 17 that a white balance adjustment is required; a color distribution axis detecting unit 20 for detecting a color distribution axis in a three-dimensional color space according to the white balance information stored in the storing unit 16 in cases where the color distribution axis is required to perform the white balance adjustment specified by the white balance adjustment mode set in the setting unit 19; a relaxation factor calculating unit 21 for calculating a relaxation factor of the white balance adjustment according to the white balance information stored in the storing unit 16 to relax the influence of the color distribution axis detected in the detecting unit 20 on the white balance adjustment; a white balance coefficient calculating unit 22 for calculating a set of white balance coefficients by using the white region detected in the detecting unit 18 and/or the color distribution axis and the relaxation factor of the white balance adjustment detected/calculated in the units 20 and 21 according to the white balance adjustment mode set in the setting unit 19, a difference between each white balance coefficient and 1.0 being reduced by the relaxation factor, and the white balance coefficients indicating a degree of the white balance adjustment; and a white balance coefficient storing unit 23 for storing the white balance coefficients calculated in the calculating unit 22. The white valance adjustment for the colored picture is performed according to the white balance coefficients in the white balance adjusting unit 14. In the white balance information extracting unit 15, as shown in FIG. 2, a colored picture is partitioned into M*N picture blocks which each are composed of a group of pixels. Each of the picture data represents a color (luminance and color differences) of one pixel, a block maximum-luminance data WP indicating a color of a maximum-luminance pixel of which a luminance value is the largest among those of pixels in one picture block is extracted from pieces of picture data in one picture block for each of the picture blocks, a block luminance minimum data BP indicating a color of a minimum-luminance pixel of which a luminance value is the smallest among those of pixels in one picture block is extracted from pieces of picture data in one picture block for each of the picture blocks, and a block average color data AVE indicating an average luminance value, an average first color difference value and an average second color difference value of an average pixel among luminance values, first color difference values and second color difference values of pixels in one picture block is extracted from pieces of picture data in one picture block for each of the picture block. Also, a piece of luminance data WPy indicating a luminance value of the block maximum-luminance data WP, a piece of first color difference data WP(r-y) indicating a first color difference value of the block maximum-luminance data WP and a piece of second color difference data WP(b-y) indicating a second color difference value of the block maximum-luminance data WP are extracted as pieces of white balance information indicating a block color feature of a maximum luminance pixel for each of the picture blocks. A first color difference is defined as a difference between a red component value r and a luminance value y of a color, and a second color difference is defined as a difference between a blue component value b and the luminance value y of a color. Also, a piece of luminance data BPy indicating a luminance value of the block luminance minimum data BP, a piece of first color difference data BP(r-y) indicating a first color difference value of the block luminance minimum data BP and a piece of second color difference data BP(b-y) indicating a second color difference value of the block luminance minimum data BP are extracted as pieces of white balance information indicating a block color feature of a minimum luminance pixel for each of the picture blocks. Also, a piece of luminance data AVEy indicating an average luminance value among luminance values of a group of pixels relating to a picture block, a piece of first color difference data AVE(r-y) indicating an average first color difference value among first color difference values of the group of pixels and a piece of second color difference data AVE(b-y) indicating an average second color difference value among second color difference values of the group of pixels are extracted as three components of the block average color data AVE to indicate a block color feature for each of the picture blocks. In addition, a piece of picture maximum-luminance data WPmax having a largest luminance value among the luminance values of the (M*N) pieces of block maximum-luminance data WP are selected, a piece of block maximum-luminance average color data WPave having an average color (luminance and color differences) among color values of the (M*N) pieces of block maximum-luminance data WP are generated, a piece of block average color maximum-luminance data AVEmax having a largest luminance value among luminance values of the (M*N) pieces of block average color data AVE are selected, and a piece of picture average color data AVEave having an average color value among the color values of the (M*N) pieces of block average color data AVE are generated. Also, a piece of luminance data WXy indicating a luminance value of the picture maximum-luminance data WPmax, a piece of first color difference data WX(r-y) indicating a first color difference value of the picture maximum-luminance data WPmax, a piece of second color difference data WX(b-y) indicating a second color difference value of the picture maximum-luminance data WPmax, a piece of squared chromaticity data WXsqc indicating a squared chromaticity (WX(r-y).sup.2 +WX(b-y).sup.2) of the picture maximum-luminance data WPmax, a piece of luminance data WAy indicating an average luminance value among luminance values of maximum-pixels respectively having a largest luminance value in a picture block, a piece of first color difference data WA(r-y) indicating an average first color difference value among first color difference values of the maximum-pixels, a piece of second color difference data WA(b-y) indicating an average second color difference value among second color difference values of the maximum-pixels, a piece of squared chromaticity data WAsqc indicating a squared chromaticity (WA(r-y).sup.2 +WA(b-y).sup.2), a piece of luminance data AXy indicating a maximum luminance value among the average luminance values respectively determined in a picture block, a piece of first color difference data AX(r-y) indicating a first color difference value of an average-pixel which has a maximum luminance value among luminance values of average-pixels respectively having an average first color difference in a picture block, a piece of second color difference data AX(b-y) indicating a second color difference value of an average-pixel which has a maximum luminance value among luminance values of average-pixels respectively having an average second color difference in a picture block, a piece of squared chromaticity data AXsqc indicating a squared chromaticity (AX(r-y).sup.2 +AX(b-y).sup.2), a piece of luminance data AAy indicating an average luminance value obtained by averaging the average luminance values respectively determined in a picture block, a piece of first color difference data AA(r-y) indicating an average first color difference value obtained by averaging the average first color difference values respectively determined in a picture block, a piece of second color difference data AA(b-y) indicating an average second color difference value obtained by averaging the average second color difference values respectively determined in a picture block and a piece of squared chromaticity data AAsqc indicating a squared chromaticity (AA(r-y).sup.2 +AA(b-y).sup.2) are extracted as the picture color information of the white balance information. In the white balance adjustment mode setting unit 19, one of first, second and third white balance adjustment modes is set. That is, only the white region detected in the detecting unit 18 is used in the first white balance adjustment mode, the color distribution axis detected in the detecting unit 20 and the relaxation factor of the white balance adjustment calculated in the calculating unit 21 are used in the second white balance adjustment mode, and the white region, the color distribution axis and the relaxation factor of the white balance adjustment detected/calculated in the 18, 20 and 21 are used in the third white balance adjustment mode. In the color distribution axis detecting unit 20, a first gravity center of the picture data (or picture signals) distributed in a three-dimensional space is calculated, and a rough color distribution axis is first defined as a line connecting an original point (or black point) of the three-dimensional space and the first gravity center. Thereafter, a cylindrical region having the rough color distribution axis as a central axis is set in the three-dimensional space, one or more pieces of outside picture data placed outside the cylindrical region are removed from the picture data because the outside picture data relate to a high chromaticity, and a second gravity center of the picture data from which the outside picture data are removed is calculated. A color distribution axis (or a white balance axis) is defined as a line connecting the original point of the three-dimensional space and the second gravity center, and the second gravity center is used as a reference point for the white balance adjustment. In the above configuration, the operation performed in the apparatus 13 for calculating a degree of white balance adjustment is described in brief with reference to FIG. 3. FIG. 3 is a flow chart showing the procedure for calculating a degree of white balance adjustment for a colored picture. In a step S101 of FIG. 3, the white balance information are extracted in the white balance information extracting unit 15. In detail, the luminance data WPy, the first color difference data WP(r-y) and the second color difference data WP(b-y) of the block maximum-luminance data WP are extracted as the white balance information of a maximum-luminance pixel for each of the picture blocks in the extracting unit 15, the luminance data BPy, the first color difference data BP(r-y) and the second color difference data BP(b-y) of the block luminance minimum data BP are extracted as the white balance information of a luminance minimum pixel for each of the picture blocks in the unit 15, and the luminance data AVEy, the first color difference data AVE(r-y) and the second color difference data AVE(b-y) of the block average color data AVE are extracted as the white balance information of an average color pixel for each of the picture blocks in the unit 15. That is, three types of color data indicating color features of each picture block are stored as the block color information of the white balance information in the white balance information storing unit 16. Also, the luminance data WXy, the first color difference data WX(r-y), the second color difference data WX(b-y) and the squared chromaticity data WXsqc of the picture maximum-luminance data WPmax are extracted as the picture color information of the white balance information in the extracting unit 15, the luminance data WAy, the first color difference data WA(r-y), the second color difference data WA(b-y) and the squared chromaticity data WAsqc of the block maximum-luminance average color data WPave are extracted as the picture color information of the white balance information in the extracting unit 15, the luminance data AXy, the first color difference data AX(r-y), the second color difference data AX(b-y) and the squared chromaticity data AXsqc of the block average color maximum-luminance data AVEmax are extracted as the picture color information of the white balance information in the extracting unit 15, and the luminance data AAy, the first color difference data AA(r-y), the second color difference data AA(b-y) and the squared chromaticity data AAsqc of the picture average color data AVEave are extracted as the picture color information of the white balance information in the extracting unit 15. The picture color information indicate the entire picture color features and are stored in the storing unit 16. In a step S102 of FIG. 3, a chromaticity strength of the colored picture is judged in the white balance adjustment judging unit 17 to judge whether or not a white balance adjustment for the colored picture is required. In cases where a major portion of the colored picture is occupied by a chromatic colored object, it is difficult to perform the white balance adjustment. Therefore, in this case, the white balance adjustment is stopped. Also, in cases where the white balance of the colored picture is sufficiently kept, it is judged that the white balance adjustment is not required. To perform the judgement of the white balance adjustment, the squared chromaticity data WXsqc, WAsqc, AXsqc and AAsqc in the picture color information of the white balance information indicating the entire picture color features are used. In cases where it is judged that the white balance adjustment is required, the procedure proceeds to a step S103. In the step S103, it is judged in the white region judging and detecting unit 18 whether or not a white region to be used as a basis of the white balance adjustment exists in one of the picture blocks. The judgement is performed by using the picture maximum-luminance data WPmax or the block average color maximum-luminance data AVEmax in the picture color information of the white balance information indicating the entire picture color features. In cases where it is judged that a piece of picture data or a picture block corresponding to the picture maximum-luminance data WPmax or the block average color maximum-luminance data AVEmax has a sufficiently low chromaticity, the existence of a white region is judged in the detecting unit 18, and the first white balance adjustment mode is set in the white balance adjustment mode setting unit 19 (a step S104). That is, a sufficiently low chromatic color of the picture data or the block data is made white in the white balance adjustment performed in the adjusting unit 14 while using a set of white balance coefficients calculated in the calculating unit 22 without performing the detection of any color distribution axis in the detecting unit 20. Also, in cases where it is judged that a piece of picture data or a picture block corresponding to the picture maximum-luminance data WPmax has a low chromaticity, the existence of a region having a color near to white is judged, and the third white balance adjustment mode is set in the white balance adjustment mode setting unit 19 (a step S104). That is, a set of white balance coefficients is calculated in the calculating unit 22 by considering RGB values of the picture maximum-luminance data WPmax and a color distribution axis detected in the detecting unit 20 to perform a white balance adjustment for the colored picture in the adjusting unit 14. In the step S104, a white balance adjustment mode is set in the setting unit 19. In cases where a white region is detected in the step S103, the first or third white balance adjustment mode is set, and the procedure jumps to a step S107 when the first white balance adjustment mode is set. In contrast, in cases where any white region is not detected in the step S103, the second white balance adjustment mode is set. Thereafter, when the second or third white balance adjustment mode is set, the detection of a color distribution axis is performed in the color distribution axis detecting unit 20 (step S105). In the S105, a color distribution axis (or a white balance axis) connecting the original point of the three-dimensional space and a reference point for a white balance adjustment placed in a gravity center of the picture data from which one or more picture data having high chromaticity are removed is detected. Thereafter, in a step S106, the calculation of a relaxation factor is performed in the relaxation factor calculating unit 21. To prevent an erroneous detection of a color distribution axis caused when a chromatic colored object considerably influences on the colored picture, a relaxation factor is calculated in the calculating unit 21 according to the block maximum-luminance average color data WPave, the block average color maximum-luminance data AVEmax and the picture average color data AVEave in the picture color information of the white balance information indicating the entire picture color features. Thereafter, an angle between the white balance axis and an achromatic axis in the three-dimensional space is decreased according to a value of the relaxation factor to relax a degree of the white balance of the colored picture. In a step S107, a set of white balance coefficients is calculated in the white balance coefficient calculating unit 109. In cases where the third white balance adjusting mode is set in the step S104, the white region detected in the step S103 is considered. That is, an intermediate point between coordinates of the white region in the three-dimensional space and the reference point for the white balance determined in the step S105 are set as a new reference point for the white balance of the colored picture. Thereafter, the white balance coefficients denoting amplification gains for colors of the pixels of the colored picture are calculated to place the white balance reference point on the achromatic axis in case of the second white balance adjusting mode or to place the new white balance reference point on the achromatic axis in case of the third white balance adjusting mode. Next, the operation performed in the apparatus 13 is described in detail. The block color information of the white balance information extracted in the step 102 are formulated as follows. the block maximum-luminance data: WP=(WPy,WP(r-y),WP(b-y)) the luminance data: WPy(m,n)=max(y(i,j)) the first color difference data: WP(r-y) (m, n )=(r-y) (i-max, j-max) the second color difference data: WP(b-y)(m,n)=(b-y)(i-max,j-max) the block luminance minimum data: BP=(BPy,BP(r-y),BP(b-y)) the luminance data: BPy(m,n)=min(y(i,j)) the first color difference data: BP(r-y)(m,n)=(r-y)(i-min,j-min) the second color difference data: BP(b-y)(m,n)=(b-y)(i-min,j-min) the block average color data: AVE=(AVEy,AVE(r-y),AVE(b-y)) the luminance data: AVEy(m,n)=.SIGMA..sub.i .SIGMA..sub.j y(i,j)/(SUM-PIX) the first color difference data: AVE(r-y)(m,n)=.SIGMA..sub.i .SIGMA..sub.j (r-y)(i,j)/(SUM-PIX) the second color difference data: AVE(b-y)(m,n)=.SIGMA..sub.i .SIGMA..sub.j (b-y)(i,j)/(SUM-PIX) Here, (m,n) denotes the number of the picture block, (i,j) denotes the numbers of the pixels placed in a picture block, y(i,j) denotes luminance values of the pixels specified by the pixel numbers (i,j), (i-max,j-max) denotes the number of a maximum-pixel having a largest luminance value among luminance values of pixels for each picture block, (i-min,j-min) denotes the number of a minimum-pixel having a smallest luminance value among luminance values of pixels for each picture block, SUM-PIX denotes the number of pixels in a picture block, max() denotes a maximum calculation, and min() denotes a minimum calculation. As a color space in which a color used as a basis of the white balance adjustment is calculated, a red-green-blue (RGB) space and a luminance-color differences space are well-known. In this embodiment, the RGB space is adopted. Therefore, luminance values and color difference values of picture signals (or picture data) are converted into red values, green values and blue values (RGB values), and the RGB values are stored in the picture memory 12. In this case, the white balance information extracted in the step 102 are formulated as follows. the block maximum-luminance data: WP=(WPr,WPg,WPb) the red data: WPr(m,n)=WP(r-y)+WPy the blue data: WPb(m,n)=WP(b-y)+WPy the green data: WPg(m,n)=(WPy-0.3*WPr-0.11*WPb)/0.59 the block luminance minimum data: BP=(BPr,BPg,BPb) the red data: BPr(m,n)=BP(r-y)+BPy the blue data: BPb(m,n)=BP(b-y)+BPy the green data: BPg(m,n)=(BPy-0.3*BPr-0.11*BPb)/0.59 the block average color data: AVE=(AVEr,AVEg,AVEb) the red data: AVEr(m,n)=AVE(r-y)+AVEy the blue data: AVEb(m,n)=AVE(b-y)+AVEy the green data: AVEg(m,n)=(AVEy-0.3*AVEr-0.11*AVEb)/0.59 Also, the picture color information of the white balance information extracted in the step 102 are formulated as follows. the picture maximum-luminance data: wPmax=(WXy,WX(r-y),WX(b-y)) the luminance data: WXy=max(WPy(m,n)) the first color difference data: WX(r-y)=WP(r-y)(m-wx,n-wx) the second color difference data: WX(b-y)=WP(b-y)(m-wx,n-wx) the squared chromaticity data: WXsqc=WX(r-y).sup.2 +WX(b-y).sup.2 the block maximum-luminance average color data: WPave=(WAy,WA(r-y),WA(b-y)) the luminance data: WAy-.SIGMA..sub.m .SIGMA..sub.n WPy(m,n)/MN the first color difference data: WA(r-y)=.SIGMA..sub.m .SIGMA..sub.n WP(r-y)(m,n)/MN the second color difference data: WA(b-y)=.SIGMA..sub.m .SIGMA..sub.n WP(b-y)(m,n)/MN the squared chromaticity data: WAsqc=WA(r-y).sup.2 +WA(b-y).sup.2 the block average color maximum-luminance data: AVEmax=(AXy,AX(r-y),AX(b-y)) the luminance data: AXy=max(AVEy(m,n)) the first color difference data: AX(r-y)=AVE(r-y)(m-ax,n-ax) the second color difference data: AX(b-y)=AVE(b-y)(m-ax,n-ax) the squared chromaticity data: AXsqc=AX(r-y).sup.2 +AX(b-y).sup.2 the picture average color data: AVEave=(AAy,AA(r-y),AA(b-y)) the luminance data: AAy=.SIGMA..sub.m .SIGMA..sub.n AVEy(m,n)/MN the first color difference data: AA(r-y)=.SIGMA..sub.m .SIGMA..sub.n AVE(r-y)(m,n)/MN the second color difference data: AA(b-y)=.SIGMA..sub.m .SIGMA..sub.n AVE(b-y)(m,n)/MN the squared chromaticity data: AAsqc=AA(r-y).sup.2 +AA(b-y).sup.2 Here, (m,n) denotes the numbers of the picture blocks, (m-wx,n-wx) denotes the number of a maximum-pixel having a largest luminance value among luminance values of the maximum-pixels specified by the pixel numbers (i-max,j-max) in the entire colored picture, MN denotes the number of picture blocks, (m-ax,n-ax) denotes the number of an average-pixel having a largest luminance value among luminance values of average-pixels which each have an average color difference value in a picture block. A chromaticity of a picture data in the RGB space is defined as a distance between an achromatic axis and the picture data in a RGB cubic color space. However, in this embodiment, a sum (r-y).sup.2 +(b-y).sup.2 of a square of a first color difference value (r-y) and a square of a second color difference value (b-y) is treated as a chromaticity value squared for convenience. However, it is applicable that a distance between an achromatic axis and a picture data be calculated as a chromaticity value of the picture data. In the step S102 of FIG. 3, each of the squared chromaticity data WAsqc, AXsqc and AAsqc is compared with a threshold value, and a colored picture in which a white balance adjustment is difficult because a chromatic colored object strongly influences on the white balance adjustment or a color picture in which any white balance adjustment is not required because the white balance in the colored picture is sufficient is detected. When a high chrominance colored object is detected, the white balance adjustment is stopped. In detail, in cases where a first condition that the squared chromaticity data WAsqc of the block maximum-luminance average color data WPave is equal to or larger than a prescribed threshold, a second condition that the squared chromaticity data AXsqc of the block average color maximum-luminance data AVEmax is equal to or larger than a prescribed threshold and a third condition that the squared chromaticity data AAsqc of the picture average color data AVEave is equal to or larger than a prescribed threshold are satisfied, a chromaticity of the colored picture is extremely high, and there is a high probability that the white balance adjustment is erroneously performed in the white balance adjusting unit 14. Therefore, the white balance adjustment is stopped. The first to third condition are formulated as follows. Here, WAth denotes a threshold for the squared chromaticity data WAsqc, AXth denotes a threshold for the squared chromaticity data AXsqc, AAth denotes a threshold for the squared chromaticity data AAsqc, and is satisfied. Though the probability that the white balance adjustment is erroneously performed is lowered as the thresholds AXth, WAth and AAth are decreased, the effect of the white balance adjustment is reduced. Also, because a relationship among the squared chromaticity data WAsqc, AXsqc and AAsqc is generally expressed as follows: the relationship AXth.gtoreq.WAth.gtoreq.AAth of the thresholds is determined. Also, in cases where the squared chromaticity data WXsqc of the picture maximum-luminance data WPmax and the squared chromaticity data WAsqc of the block maximum-luminance average color data WPave are sufficiently low, the picture data of the colored picture are almost placed on the achromatic axis. In this case, because the white balance of the colored picture is sufficient, any white balance adjustment is not performed. That is, in cases where are satisfied, any white balance adjustment is not performed. Here, WAXmax denotes an upper limit threshold for the squared chromaticity data WXsqc and WAsqc. In the step S103 of FIG. 3, it is judged in the white region detecting unit 18 whether or not a white region to be used as a basis of the white balance adjustment exists in one of the picture blocks according to the white balance information. As one of ideas for the white balance adjustment, a pixel (or a region) which seems to be the most appropriate for white (or an achromatic color) is detected from a colored picture, and the pixel (or the region) is set to white (or the achromatic color). In cases where a viewer watches a colored picture, the viewer pays attention to a white object of the colored picture as a basis for judging whether or not the white balance of the colored picture is appropriately adjusted. For example, even though a color of a chromatic colored object is not correctly reproduced in a colored picture, a viewer is difficult to feel that the color of the chromatic colored object is not correctly reproduced. In contrast, even though an achromatic colored object is slightly colored, the viewer can easily feel that the colored achromatic object is strange. Therefore, prior to the detection of a color distribution axis, the white region judgement is performed by using the picture maximum-luminance data WPmax and the block average color maximum-luminance data AVEmax of the white balance information, and a white balance adjustment is performed in the adjusting unit 14 to make white (or an achromatic color) a sufficiently low chromatic color of a piece of picture data or a picture block corresponding to the picture maximum-luminance data WPmax or the block average color maximum-luminance data AVEmax in cases where it is judged in the detecting unit 18 that the picture block includes a white object (or an achromatic colored object). Initially, it is judged whether or not a pixel which relates to a piece of picture data corresponding to the picture maximum-luminance data WPmax is equivalent to a white region. In cases where a major portion of a colored picture is not occupied by any chromatic colored object having a high chromaticity, a color distribution of pieces of picture data of the colored picture is formed in a spindle shape which extends in a luminance direction in a three-dimensional color space. Also, in cases where a white balance is kept in the colored picture, a major-component axis of the color distribution for the colored picture almost agrees with an achromatic color axis of the color space. In contrast, in cases where a white balance is not kept in the colored picture, for example, because of the influence of a light source illuminating an object, a major-component axis of the color distribution for the colored picture agrees with a straight line passing through an original point of the color space which crosses the achromatic color axis at an angle. In any case, a top portion of the spindle-shaped color distribution in a high luminance direction is placed at a position of a piece of picture data corresponding to the picture maximum-luminance data WPmax. That is, in cases where the color distribution is formed in the spindle shape extending in a luminance direction, a piece of picture data placed at a top portion of the color distribution in a high luminance direction agrees with the picture maximum-luminance data WPmax. Therefore, the picture maximum-luminance data WPmax can be used as a piece of reference data for the white balance adjustment. In this embodiment, a block distance dis-wp between the block maximum-luminance data WP and the original point of the color space is determined for each of the picture blocks, and when a piece of block maximum-luminance data WP corresponding to a maximum block distance which is the largest among the M*N block distances dis-wp agrees with the picture maximum-luminance data WPmax, it is judged in the detecting unit 18 that a pixel or a picture block which relates to a piece of picture data corresponding to the picture maximum-luminance data WPmax is equivalent to a white region or a region having a color near to white, and a set of white balance coefficients is calculated in the calculating unit 22 while considering the picture maximum-luminance data WPmax and a detecting result of a color distribution axis (the third white balance adjustment mode). The judgement of a white color region is formulated as follows. the block distance: dis-wp(m,n)=(WPr(m,n).sup.2 +WPg(m,n).sup.2 +WPb(m,n).sup.2).sup.1/2 the maximum block distance: dis-max=max(dis-wp(m,n)) A maximum distance between the picture maximum-luminance data WPmax and the original point of the color space: If dis-max=dis-wx is satisfied, the picture maximum-luminance data WPmax is considered for the white balance adjustment. In addition, when a luminance value of the picture maximum-luminance data WPmax is sufficiently high, a probability that a piece of picture data corresponding to the picture maximum-luminance data WPmax indicates a white region is heightened. Therefore, a first condition that dis-max=dis-wx is satisfied and a second condition that the luminance value WXy of the picture maximum-luminance data WPmax is higher than a prescribed threshold WXYmax (WXy>WXYmax), it is judged in the setting unit 19 that a pixel which relates to a piece of picture data corresponding to the picture maximum-luminance data WPmax is equivalent to a white region, a set of white balance coefficients is calculated in the calculating unit 22 by only considering the picture maximum-luminance data WPmax (the first white balance adjustment mode). In this embodiment, the block distance between the original point and the block maximum-luminance data WP is calculated. However, it is applicable that a block distance between a piece of particular data having a smallest luminance value among the luminance values BPy of the M*N pieces of block luminance minimum data BP and the block maximum-luminance data WP be calculated for each of the picture blocks. Also, the square root calculation is performed in this embodiment to obtain the block distances dis-wp and the maximum distance dis-wx. However, it is applicable that a distance squared be calculated. Also, it is applicable that a simplified block distance: be calculated in place of the block distance dis-wp for convenience. Thereafter, in cases where it is judged in the detecting unit 18 that a piece of picture data corresponding to the picture maximum-luminance data WPmax does not indicate a white region, it is judged in the detecting unit 18 whether or not a pixel which relates to a piece of picture data corresponding to the block average color maximum-luminance data AVEmax is equivalent to a white region. Even though the picture maximum-luminance data WPmax does not indicate the existence of a white region, there is a case that the block average color maximum-luminance data AVEmax indicates the existence of a white region. In detail, a first condition that the squared chromaticity data AXsqc of the block average color maximum-luminance data AVEmax is lower than the squared chromaticity data WAsqc of the block maximum-luminance average color data WPave (AXsqc<WAsqc) and a second condition that the squared chromaticity data AXsqc is lower than a prescribed threshold AX-WBC (AXsqc <AX-WBC) are considered, and when the first and second conditions are satisfied, the white balance adjustment is performed in the adjusting unit 14 by only considering the block average color maximum-luminance data AVEmax (the first white mode adjustment mode). The first condition (AXsqc<WAsqc) is added to heighten the reliability that a piece of picture data corresponding to the block average color maximum-luminance data AVEmax indicates the existence of a white region. Thereafter, in cases where the condition dis-max=dis-wx and WXy>WXYmax is satisfied, a first white balance adjustment mode signal is sent from the detecting unit 18 to the white balance mode setting unit 19 to select the first white balance adjustment mode in the step S104 of FIG. 3, and a piece of white region data Dwr represented by RGB values (WXr, WXg, WXb) of the picture maximum-luminance data WPmax is transferred to the white balance coefficient calculating unit 22. Also, in cases where the condition AXsqc<WAsqc and AXsqc <AX-WBC is satisfied, the first white balance adjustment mode signal is sent to the setting unit 19 in the same manner, and a piece of white region data Dwr represented by RGB values (AVEr, AVEg, AVEb) of the block average color maximum-luminance data AVEmax is transferred to the calculating unit 22. Thereafter, the procedure jumps to a step S107. In contrast, in cases where the condition dis-max=dis-wx and WXy.ltoreq.WXYmax is satisfied, a third white balance adjustment mode signal is sent from the detecting unit 18 to the setting unit 19 to select the third white balance adjustment mode in the step s104, and a piece of white region data Dwr represented by RGB values (WXr, WXg, WXb) of the picture maximum-luminance data WPmax is transferred to the calculating unit 22. Thereafter, the procedure proceeds to the step S105. In other cases, any white region used as a basis of a white balance adjustment is not detected in the detecting unit 18, a second white balance adjustment mode signal is sent from the detecting unit 18 to the setting unit 19 to select the second white balance adjustment mode in the step S104, and any piece of white region data is not transferred to the calculating unit 22. Thereafter, the procedure proceeds to the step S105. In the present invention, the assumption that an integrated value (or an average value) of color difference signals for a picture in which an appropriate white balance is kept becomes zero is extended for a colored picture in a three-dimensional color space, and a degree of white balance adjustment for the colored picture is calculated in the apparatus 13 on a second assumption that a major component axis of a three-dimensional color distribution for a colored picture in which a white balance is appropriately kept agrees with an achromatic color axis. Therefore, a method for analyzing major components is preferable in the step S105 of FIG. 3 to detect a color distribution axis of the color distribution. However, in this embodiment, it is assumed that a gravity center of the color distribution is placed on a major component axis of the color distribution, a gravity center of the color distribution is calculated, and a vector from the original point of the color space to a gravity center of the color distribution is defined as a color distribution axis vector. Also, because the second assumption is not correct in a case that a major portion of a colored picture is occupied by an object having a high chromatic color, in the same manner as the assumption that the integrated value of color difference signals becomes zero, it is requited in the step S105 to cope with the case that a major portion of a colored picture is occupied by an object having a high chromatic color. Therefore, to perform the detection of a color distribution axis by removing the influence of an object having a high chromatic color, there is a suggestion that a cylindrical region having an achromatic color axis of a RGB space as a central axis is set to obtain a gravity center of pieces of picture data existing in the cylindrical region as a gravity center of a color distribution for a colored picture. However, in cases where a major-component axis of the color distribution does not agree with an achromatic color axis of the RGB space, even though the picture data existing in the cylindrical region are selected to determine a gravity center of the color distribution, the determined gravity center of the color distribution is not placed on the achromatic color axis of the RGB space, and the adverse influence of the object having a high chromatic color cannot be removed. The reason is that absolute chromaticity values of the picture data are not correct because the white balance for the colored picture is not kept. In this embodiment, to perform the detection of a color distribution axis by removing the influence of an object having a high chromatic color, a rough color distribution axis roughly indicating an one-sided degree of the color distribution of the picture data in a three-dimensional color space is initially calculated. The rough color distribution axis is called a first-stage color distribution axis. Thereafter, a cylindrical region having the first-stage color distribution axis as a central axis is set, pieces of picture data placed outside the cylindrical region are removed because the outside picture data are regarded to indicate an object having a high chromaticity, and a second-stage color distribution axis is detected in the detecting unit 20 by using pieces of picture data placed inside the cylindrical region. FIG. 4 is a block diagram of the color distribution axis detecting unit 20 shown in FIG. 1. As shown in FIG. 4, the color distribution axis detecting unit 20 comprises a first-stage color distribution axis calculating unit 31 for synthesizing two two-dimensional color distribution axes detected in two two-dimensional color planes of a three-dimensional RGB color space and calculating a three-dimensional rough color distribution axis in the color space as a first-stage color distribution axis, and a second-stage color distribution axis calculating unit 32 for setting a cylindrical region having the second-stage color distribution axis as a central axis and calculating a second-stage color distribution axis by using pieces of picture data placed inside the cylindrical region. The first-stage color distribution axis calculating unit 31 comprises: a histogram memory number calculating unit 33 for calculating reference memory numbers of a green-red (GR) two-dimensional histogram and reference memory numbers of a green-blue (GB) two-dimensional histogram according to red, green and blue values of the block maximum-luminance data WP, the block average color data AVE and the block luminance minimum data BP stored in the white balance information storing unit 16; a removing block detecting unit 34 for detecting a picture block composed of a group of pixels having a uniform chromatic color by comparing the block average color data AVE and the block luminance minimum data BP for each of the picture blocks to remove the picture block detected; a GR histogram calculating unit 35 for calculating a GR two-dimensional histogram for green and red values of the block maximum-luminance data WP, the block average color data AVE and the block luminance minimum data BP, the block maximum-luminance data WP corresponding to all of the picture blocks, the block average color data AVE corresponding to picture blocks which are not removed in the removing block detecting unit 34, the block luminance minimum data BP corresponding to picture blocks which are not removed in the removing block detecting unit 34, and the green and red values of the data WP, AVE and BP being indicated by the reference memory numbers calculated in the histogram memory number calculating unit 33; a GB histogram calculating unit 36 for calculating a GB two-dimensional histogram for green and blue values of the block maximum-luminance data WP, the block average color data AVE and the block luminance minimum data BP, the block maximum-luminance data WP corresponding to all of the picture blocks, the block average color data AVE corresponding to picture blocks which are not removed in the removing block detecting unit 34, the block luminance minimum data BP corresponding to picture blocks which are not removed in the removing block detecting unit 34, and the green and blue values of the data WP, AVE and BP being indicated by the reference memory numbers calculated in the histogram memory number calculating unit 33; a GR plane color distribution axis calculating unit 37 for calculating a GR two-dimensional color distribution axis in a GR plane by using the GR two-dimensional histogram calculated in the GR histogram calculating unit 35; a GB plane color distribution axis calculating unit 38 for calculating a GB two-dimensional color distribution axis in a GB plane-by using the GB two-dimensional histogram calculated in the GB histogram calculating unit 36; an angle table read only memory (ROM) 39 for storing a plurality of GR angles respectively indicating an angle between a straight line connecting a point of the GR two-dimensional plane and an original point of the GR two-dimensional plane and a green axis of the GR two-dimensional plane and storing a plurality of GB angles respectively indicating an angle between a straight line connecting a point of the GB two-dimensional plane and the original point of the GB two-dimensional plane and the green axis of the GR two-dimensional plane; a weighting table ROM 40 for storing a plurality of weighting factors corresponding to the GR and GB angles stored in the angle table ROM 39 to obtain weighted average angles in the GR plane color distribution axis calculating unit 37 and the GB plane color distribution axis calculating unit 38 in a weighted average angle calculation; and a three-dimensional color distribution axis synthesizing unit 41 for synthesizing the two-dimensional GR color distribution axis output from the GR plane color distribution axis calculating unit 37 and the two-dimensional GB color distribution axis output from the GB plane color distribution axis calculating unit 38 and calculating a three-dimensional first-stage color distribution axis. The second-stage color distribution axis calculating unit comprises: a wP block data gravity center calculating unit 42 for setting a cylindrical region having the first-stage color distribution axis calculated in the color distribution axis synthesizing unit 41 as a central axis in the RGB color space and calculating a gravity center of pieces of block maximum-luminance data WP placed in the cylindrical region of the RGB color space; an AVE block data gravity center calculating unit 43 for setting a cylindrical region having the first-stage color distribution axis calculated in the color distribution axis synthesizing unit 41 as a central axis in the RGB color space and calculating a gravity center of pieces of block average color data AVE placed in the cylindrical region of the RGB color space; and an average value calculating unit 44 for averaging the gravity center of the block maximum-luminance data WP calculated in the WP block data gravity center calculating unit 42 and the gravity center of the block average color data AVE calculated in the AVE block data gravity center calculating unit 43 to obtain an average point in the RGB color space and calculating a second-stage color distribution axis connecting the original point of the RGB color space and the average point. In the above configuration, an operation of the first-stage color distribution axis calculating unit 31 is described with reference to FIG. 5. FIG. 5 is a flow chart showing the operation performed in the first-stage color distribution axis calculating unit 31. As shown in FIG. 5, in a step S201, the block maximum-luminance data WP(WPr,WPg,WPb), the block average color data AVE(AVEr,AVEg,AVEb) and the block luminance minimum data BP(BPr,BPg,BPb) for a particular picture block are transferred from the white balance information storing unit 16 to the histogram memory number calculating unit 33. In a step S202, reference memory numbers of a GR two-dimensional histogram and reference memory numbers of a GB two-dimensional histogram are calculated in the calculating unit 33. The GR two-dimensional histogram is defined as a two-dimensional color distribution obtained by projecting a three-dimensional color distribution defined in the RGB color space onto a GR plane, and the GB two-dimensional histogram is defined as a two-dimensional color distribution obtained by projecting a three-dimensional color distribution defined in the RGB color space onto a GB plane. In this embodiment, to reduce a memory volume required to store the red values, the green values and the blue values (RGB values) of the data WP,AVE and BP, a luminance range (0 to 255) for each of red, green and blue components is partitioned into 16 groups (0 to 15, 16 to 31, - - -, 240 to 255). That is, red, green and blue components of each of the block maximum-luminance data WP, the block average color data AVE and the block luminance minimum data BP are expressed as follows by using reference memory numbers hr (hr=0 to 15) of the red component, reference memory numbers hg (hg=0 to 15) of the green component and reference memory numbers hb (hb=0 to 15) of the blue component. WP(hr, hg, hb)=(WPr/16, WPg/16, WPb/16) AVE(hr, hg, hb)=(AVEr/16, AVEg/16, AVEb/16) BP(hr, hg, hb)=(BPr/16, BPg/16, BPb/16) In this case, reference memory numbers of each of two-dimensional histograms GR-hist(hg, hr) and GB-hist(hg, hb) are indicated by a two-dimensional 16*16 matrix. That is, each component of the 16*16 matrix in the GR or GB two-dimensional histogram indicates the frequency of particular sets (hg, hr) or (hg, hb) of reference memory numbers of the data WP, AVE and BP. In a step S203, a GR two-dimensional histogram GR-hist(hg, hr) is calculated in the GR histogram calculating unit 35 by counting a set (hg,hr) of reference memory numbers hg and hr of the block maximum-luminance data WP calculated in the calculating unit 33 for the particular picture block, and a GB two-dimensional histogram GB-hist(hg, hb) is calculated in the GB histogram calculating unit 36 by counting a set (hg, hb) of reference memory numbers hg and hb of the block maximum-luminance data WP calculated in the calculating unit 33 for the particular picture block. In a step S204, a picture block composed of a group of pixels having a uniform chromatic color is detected in the removing block detecting unit 34 by comparing the block average color data AVE and the block luminance minimum data BP with each other. When it is judged that a color indicated by the block average color data AVE for the particular picture block is similar to that of the block luminance minimum data BP for the particular picture block, a block removal flag is set to "on" to indicate the removal of the picture block. By comparing the white balance information WP, AVE and BP with each other for each of the picture blocks, color features of each picture block can be grasped in some degree. In particular, the detection of a color distribution axis is disturbed by the white balance information WP, AVE and BP which correspond to a picture block composed of a group of pixels having a uniform chromatic color or a picture block in which an object having a high chromaticity is included. In this embodiment, because the white balance information WP, AVE and BP corresponding to a picture block in which a uniform background such as a blue sky or a uniform background in a portrait is only included are almost the same as each other, the picture block having a uniform chromatic color is removed by comparing luminance, hue and chromaticity of the white balance information AVE and BP with each other. That is, a set of reference memory numbers of the white balance information AVE and BP which correspond to the picture block having a uniform chromatic color is not counted in the calculation of the GR and GB two-dimensional histograms. In this case, because the block maximum-luminance data WP is important to calculate a color distribution axis, a set of reference memory numbers of the block maximum-luminance data WP which corresponds to a picture block having a uniform chromatic color is counted in the calculation of the GR and GB two-dimensional histograms. However, it is applicable that the block maximum-luminance data WP of a picture block having a uniform chromatic color be not considered for the calculation of a color distribution axis. In the judgement of the pict |