Color image processing apparatus for extracting image data having predetermined color information from among inputted image data and for correcting inputted image data in response to the extracted image data

• US 5,130,935 A
• Filed: 09/14/1989
• Issued: 07/14/1992
• Est. Priority Date: 03/31/1986
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takiguchi, Hideo
• Primary Examiner(s): Dixon, Joseph L.
• Application Number:
  US07/408,424
• Time in Patent Office: 1,034 Days
• Field of Search: 364/526, 364/570, 364/571.02, 340/701, 382/17, 382/19, 358/75, 358/80, 356/407, 356/408
• US Class Current: 382/167
• CPC Class Codes: H04N 1/62 Retouching, i.e. modification of isolated colours only or in isolated picture areas only
• CPC Class Codes: H04N 1/628 Memory colours, e.g. skin or sky

Abstract

A color image processing apparatus generates color image data, measures the quantity of the image data within a predetermined region of color space, obtains a representative color value for the image data within that region, and corrects the color image data based on the representative value and the measured quantity.

The number of image data which exist within a predetermined region on a (u,v), chromaticity diagram and which are among input color image data is counted. When the counted number is smaller than a predetermined value, the correcting operation is not executed. The difference between a predetermined coordinate point and a coordinate point at which the largest counted number of image data exist is obtained, and by the obtained distance either all the image data or the image data within the predetermined region are corrected.

Claims

1. A color image processing apparatus comprising:

generating means for generating color image data;

measuring means for measuring a number of image data which represent color belonging to a predetermined region of color space and which are generated by said generating means;

means for obtaining a representative value of color of the image data within said predetermined region;

means for correcting chromaticity of the color image data based on said representative value and said number measured by said measuring means; and

means for outputting the corrected color image data to a color image reproducing device.

2. The color image processing apparatus according to claim 1, wherein said correction means corrects the image data when said number is more than a predetermined value.

3. The color image processing apparatus according to claim 1, wherein said correction means determines a correction quantity of the image data based on a difference between said representative value and a reference color.

4. The color image processing apparatus according to claim 1, wherein said correction means corrects all of said image data.

5. The color image processing apparatus according to claim 1, wherein said correction means corrects color image data which represent color within said predetermined region.

6. The color image processing apparatus according to claim 1, wherein said correction means corrects color image data that represent color within an extended region including said predetermined region.

7. The color image processing apparatus according to claim 1, wherein said representative value is a value of color having a maximum appearance within said predetermined region.

8. The color image processing apparatus according to claim 1, wherein said color within said predetermined region is a skin color.

9. The color image processing apparatus according to claim 1, wherein said color image data is represented by L*, u and v.

10. The color image processing apparatus for processing input image data and outputting process image data, comprising:

measuring means for measuring a number of image data which represent color belonging to a predetermined region of color space;

means for judging if color correction is to be performed, based on whether said number measured by said measuring means is more than a predetermined quantity;

means for determining a reference correction quantity when said judging means judges that color correction is to be performed, based on a difference of said image data from a reference chromaticity determined previously with respect to said predetermined region;

means for correcting chromaticity of said image data using said reference correction quantity added with a weight corresponding to a color distance of said image data from said reference chromaticity; and

means for outputting the corrected image data to a color image reproducing device.

11. The color image processing apparatus according to claim 10, wherein said difference of said image data from said reference chromaticity is a deviation of a color having a maximum noticeability among colors having chromaticity within said predetermined region from said reference chromaticity.

12. The color image processing apparatus according to claim 10, wherein said color within said predetermined region is a skin color.

13. A color image processing apparatus according to claim 10, wherein said image data is represented by L*, u and v.

14. A color image processing apparatus comprising:

converting means for converting input color image data into luminance chromaticity information;

counting means for counting a number of color image data representing color within a predetermined region in color space;

means for recognizing, in response to a count value counted by said counting means, a coordinate point at which a largest number of color image data are distributed in said predetermined region as a representative value;

correcting means for determining a distance between a hue represented by a representative value and a predetermined hue and for correcting chromaticity of said input image data based on said determined distance as a correction quantity; and

means for outputting the corrected color image data to a color image reproducing device.

15. The color image processing apparatus according to claim 14, wherein when the number of said color image data counted by said counting means is larger than a predetermined value, said correcting means executes its correcting operation, and when the number of said color image data counted by said counting means is smaller than said predetermined value, said correcting means does not execute its correcting operation.

16. The color image processing apparatus according to claim 14, wherein said predetermined region is divided into a plurality of partial areas, wherein the number of color image data which exist in each of said partial areas is counted, and wherein a coordinate point of one of said partial areas corresponding to the largest number among the counted numbers is recognized as said representative value.

17. The color image processing apparatus according to claim 14, wherein said color space plane is represented by u and v, and all the image data are represented by u_n and v_n, and wherein said correction quantity (u_n '"'"', v_n '"'"') is obtained as follows:

space="preserve" listing-type="equation">u.sub.n '"'"'=u.sub.n -Δ

u

space="preserve" listing-type="equation">v.sub.n '"'"'=v.sub.n -Δ

v

wherein a difference (Δ

u, Δ

v) between said representative value, represented as (u₁, v₁), and an intersection (u₀, v₀) of a line of said predetermined hue with a perpendicular drawn from a coordinate of said representative value (u₁, v₁) toward the line is obtained by Δ

u=u₁ -u₀ and Δ

v=v₁ -v₀.

18. The color image processing apparatus according to claim 14, wherein said correcting means corrects input image data in said predetermined region.

19. The color image processing apparatus according to claim 14, wherein a color of said predetermined region is a skin color.

20. A color image processing apparatus comprising:

converting means for converting input color image data into luminance chromaticity information;

counting means for counting a number of color image data representing color within a predetermined region in color space;

means for recognizing, in response to a count value counted by said counting means, a coordinate point at which a largest number of color image data are distributed in said predetermined region as a representative value;

means for determining a distance between said representative value and predetermined reference value and for recognizing said distance as a correction quantity;

correcting means for executing a weighting operation with a weight obtained in response to a distance between image data to be corrected and said reference value and for correcting chromaticity of said input image data, wherein said correction quantity is allowed to be changed in response to said weight; and

means for outputting the corrected image data to a color image reproducing device.

21. The color image processing apparatus according to claim 20, wherein when the number of said color image data counted by said counting means is larger than a predetermined value, said correcting means executes its correcting operation, and when the number of said color image data counted by said counting means is smaller than said predetermined value, said correcting means does not execute its correcting operation.

22. The color image processing apparatus according to claim 20, wherein said predetermined region is divided into a plurality of partial areas, wherein a number of color image data which exist in each of said partial areas is counted, and wherein a coordinate point of one of said partial areas corresponding to a largest number among the counted numbers is recognized as said representative value.

23. The color image processing apparatus according to claim 20, wherein said chromaticity plane is represented by u and v, and a difference (Δ

u, Δ

v) between said representative value (u₁, v₁) and an intersection (u₀, v₀) of a line of said predetermined hue with a perpendicular drawn from a coordinate of said representative value (u₁, v₁) toward the line is recognized as said correction quantity.

24. The color image processing apparatus according to claim 20, wherein said correcting means executes a correcting operation as follows:

space="preserve" listing-type="equation">u.sub.n '"'"'=u.sub.n -Δ

u

space="preserve" listing-type="equation">v.sub.n '"'"'=v.sub.n -Δ

v

wherein (u_n, v_n) represents input image data in said predetermined region, (Δ

u, Δ

v) represents said correction quantity and (u_n '"'"', v_n '"'"') represents said representative value.

25. The color image processing apparatus according to claim 20, wherein said correcting means executes a correcting operation within an extended region encircling said predetermined region such that, as said representative value separates from said predetermined region, said correction quantity (Δ

u, Δ

v) is decreased, and when said representative value is on an outline of said extended region, said correction quantity becomes zero, and such that said representative value (u_n '"'"', v_n '"'"') is obtained by subtracting said correction quantity (Δ

u, Δ

v) from said inputted image data (u_n v_n) as follows;

space="preserve" listing-type="equation">u.sub.n '"'"'=u.sub.n -Δ

u

space="preserve" listing-type="equation">v.sub.n '"'"'=v.sub.n -Δ

v.

26. The color image processing apparatus according to claim 20, wherein a color of said predetermined region is a skin color.

27. A color image processing method comprising the steps of:

generating color image data;

measuring a number of image data which represent color belonging to a predetermined region of color space and which are generated in said generating step;

obtaining a representative value of color of the image data within the predetermined region;

correcting chromaticity of the color image data based on the representative value and the number measured in said measuring step; and

outputting the corrected color image data to a color image reproducing device.

28. A color image processing method for processing input image data and outputting processed image data, comprising the steps of:

measuring a number of image data which represent color belonging to a predetermined region of color space;

judging if color correction is to be performed, based on whether the number measured in said measuring step is more than a predetermined quantity;

determining a reference correction quantity when it is determined in said judging step that color correction is to be performed, based on a difference of the previously with respect to the predetermined region;

correcting chromaticity of the image data using the reference correction quantity added with a weight corresponding to a color distance of the image data from the reference chromaticity; and

outputting the corrected image data to a color image reproduction device.

29. A color image processing method comprising the steps of:

converting input color image data into luminance chromaticity information;

counting a number of color image data representing color within a predetermined region in color space;

recognizing, in response to a count value counted in said counting step, a coordinate point at which a largest number of color image data are distributed in the predetermined region as a representative value;

determining a distance between a hue represented by the representative value and a predetermined hue and for correcting chromaticity of the input image data based on the determined distance as a correction quantity; and

outputting the corrected image data to a color image reproduction device.

30. A color image processing method comprising the steps of:

converting input color image data into luminance chromaticity information;

counting a number of color image data representing color within a predetermined region in color space;

recognizing, in response to a count value counted in said counting step, a coordinate point at which a largest number of color image data are distributed in the predetermined region as a representative value;

determining a distance between the representative value and a predetermined reference value and for recognizing the distance as a correction quantity;

executing a weighting operation with a weight obtained in response to a distance between image data to be corrected and the reference value and for correcting chromaticity of the input image data, wherein the correction quantity is allowed to be changed in response to the weight; and

outputting the corrected image data to a color image reproduction device.