Color chart for image correction and method of color correction

• US 5,852,675 A
• Filed: 04/15/1996
• Issued: 12/22/1998
• Est. Priority Date: 04/14/1995
• Status: Expired due to Term

• Current Assignee: Dai Nippon Printing Company Limited, Kiyoshi Matsuo
• Original Assignee: Dai Nippon Printing Company Limited, Kiyoshi Matsuo
• Inventors: Hayashi, Masaho, Matsuo, Kiyoshi, Uchida, Atsushi
• Primary Examiner(s): Voeltz, Emanuel Todd
• Assistant Examiner(s): Smithers, Matthew
• Application Number:
  US08/632,065
• Time in Patent Office: 981 Days
• Field of Search: 364/526, 382/167, 382/128, 430/11, 358/523, 358/518, 358/455
• US Class Current: 382/167
• CPC Class Codes: H04N 1/4078 using gradational references, e.g. grey-scale test pattern analysis
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence

Abstract

In order to correct for colors of images taken photographs of e.g., patient'"'"'s skin in a clinical medicine, the method of the present invention comprises a color chart for image correction including a sheet base substrate, on the back surface of which an adhesive layer capable to adhere onto an object such as the patient'"'"'s skin and color materials for example three colors R, G, B as three primary colors of lights applied on the surface to be captured in a color image with the object to correct for colors in an entire image according to basic colors indicated in the captured color regions.

Claims

1. A color chart for image correction comprised of a sheet base substrate such as paper and plastic film, in which an adhesive layer is provided in the posterior side for adhering onto an object the surface of the sheet base substrate is matted, and at least three mat color materials are applied each in a different partition on the surface of the sheet base substrate, wherein the partitions to which said color materials are applied is divided into square grids of the same number as the number of the color materials a scale is provided located around the square grid partitions on the surface of said base substrate in a form of a series of squares of a standard size.

2. The color chart for image correction as in claim 1, comprising fundamental color of at least one color system from RGB color system, CMY color system, and Lab color system in the color materials.

3. The color chart for image correction as in claim 1, further comprising at least one of white, gray, and black in the color materials.

4. The color chart for image correction as in claim 1, wherein the surface of said base substrate is formed in the form of square, an inscribed circle approximately inscribing to said square thereon is formed, and said circle is divided into quadratures, and one of zone of said quadratures of the circle and zone of the four corners of the squares outside the circle is applied with colors of three primary colors of RGB color system, three primary colors of CMY color system, fundamental colors of Lab color system, and the other is applied with at least one of white, gray, and black color materials.

5. The color chart for image correction as in claim 4, the entire square surface of the base substrate is partitioned as grids and a part of the grid is superimposed on the quadrature lines of said circle.

6. The color chart for image correction as in claim 4, at least one of quadrature circle within said circle on the surface of said base substrate is partitioned as grids and a part of the grid is superimposed on the quadrature lines of said circle.

7. The color chart for image correction as in claim 1, wherein the length of one edge of respective partitions of said grids is a standard size.

8. The color chart for image correction as in claim 1, wherein said surface of said base substrate is formed of material having roughness and color approximately identical to the surface of said object.

9. The color chart for image correction as in claim 1, wherein said surface of said base substrate is formed of material having roughness and color approximately identical to the human skin.

10. A method of color correction comprising the steps of:

recording images of a color chart for image correction comprised of a sheet base substrate such as paper and plastic film, in which an adhesive layer is provided in the posterior side for adhering onto an object, the surface of the base is matted, and at least three mat color materials are applied each in a different partition on the surface of the base substrate, along with the object by adhering thereon with said adhesive layer;

capturing said taken image into a storage device as digital data;

displaying on a display screen the digital data stored in the storage device;

reading the color values of at least two of said three colors of the color chart for image correction on the display;

computing a correcting value for each color based on the digital data of the color values of the read color chart for image correction and target values corresponding to the partitions in the color chart for image correction, and;

correcting the digital data stored in the storage device with said computed correction values to store again in the storage device.

11. The method of color correction as in claim 10, wherein said three colors are predetermined to be white, black, and gray, and the target values for these color values O_H, O_L, O_M are preselected, and wherein from the image displayed on said display RGB values for white partition I_H (R), I_H (G), I_H (B), RGB values for black partition I_L (R), I_L (G), I_L (B), and RGB values for gray partition I_M (R), I_M (G), I_M (B) are read to compute correction values on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0, 0), (I_L, O_L), (I_M, O_M), (I_H, O_H), (255, 255).

12. The method of color correction as in claim 10, wherein said three colors are predetermined to be white, black, and gray, and the target values for these color values O_H, O_L, O_M are preselected;

wherein from the image displayed on said display RGB values for white partition I_H (R), I_H (G), I_H (B), are read to convert respective RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_H, O_H), (255,

     255);

wherein from the image displayed on said display RGB values for black partition I_L (R), I_L (G), I_L (B), are read to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_L, O_L), (255,

     255); and

wherein from the image displayed on said display RGB values for gray partition I_M (R), I_M (G), I_M (B), are read to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_M, O_M), (255,

     255).

13. The method of color correction as in claim 10, wherein said three colors are predetermined to be white, black, and gray, and the target values for white and black color values O_H, O_L are preselected;

wherein from the image displayed on said display RGB values for white partition I_H (R), I_H (G), I_H (B), are read to convert respective RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_H, O_H), (255,

     255);

wherein from the image displayed on said display RGB values for black partition I_L (R), I_L (G) , I_L (B), are read to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_L, O_L), (255,

     255); and

wherein from the image displayed on said display RGB values for gray partition I_M (R), I_M (G), I_M (B), are read to compute the mean value Ave(I_M) thereof to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_M, Ave(I_M)), (255,

     255).

14. The method of color correction as in claim 10, wherein said three colors are predetermined to be white, black, and gray, and the target values for these color values O_H, O_L, O_M are preselected;

wherein from the image displayed on said display RGB values for white partition I_H (R), I_H (G), I_H (B), are read to convert respective RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_H, O_H), (255,

     255);

wherein from the image displayed on said display RGB values for black partition I_L (R), I_L (G), I_L (B), are read to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_L, O_L), (255,

     255); and

wherein RGB values of the gray partition I_M (R), I_M (G), I_M (B) are read to compute O'"'"'_M given by

space="preserve" listing-type="equation">O'"'"'.sub.M (R)=Σ

I.sub.M +(O.sub.M (R)/Σ

O.sub.M)

space="preserve" listing-type="equation">O'"'"'.sub.M (G)=Σ

I.sub.M +(O.sub.M (G)/Σ

O.sub.M)

space="preserve" listing-type="equation">O'"'"'.sub.M (B)=Σ

I.sub.M +(O.sub.M (B)/Σ

O.sub.M)

where Σ

I_M =I_M (R)+I_M (G)+I_M (B),

Σ

O_M =O_M (R)+O_M (G)+O_M (B), to convert respective converted RGB digital data on a bi-dimensional graph having the read values and said corresponding target values as coordinate axis according to a curve passing through (0,

     0), (I_M, O'"'"'_M), (255,

     255).

15. The method of color correction as in claim 10, wherein said three colors are predetermined to be white, black, and gray, and the target values for these color values O_H, O_L, O_M are preselected;

wherein L* part of the grid is value for white and black partitions of the image opened on said display, I_H (L), I_L (L), and L* a* b* values for gray partition I_M (L), I_M (a), I_M (b) are read to convert said read L* data according to a curve passing through the points (0,

     0), (I_L (L), O_L (L)), (I_M (L), O_M (L)), (I_H (L), O_H (L)), (100,

     100) on the bi-dimensional graph having these read values and the corresponding target values as coordinate axis;

wherein the correction values Δ

M(a), Δ

M(b) are calculated given by;

space="preserve" listing-type="equation">Δ

M(a)=O.sub.M (a)-I.sub.M (a), and

space="preserve" listing-type="equation">Δ

M(b)=O.sub.M (b)-I.sub.M (b),

wherein said converted digital data is converted by adding said correction values Δ

M(a), Δ

M(b) to the already captured a* and b* data respectively.