IMAGE PROCESSING APPARATUS, IMAGE PROCESSING METHOD, AND PROGRAM PRODUCT

• US 20130120431A1
• Filed: 10/31/2012
• Published: 05/16/2013
• Est. Priority Date: 11/16/2011
• Status: Active Grant

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: KAWAGUCHI, Hirofumi
• Granted Patent: US 9,214,010 B2
• Time in Patent Office: Days
• US Class Current: 345/590
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 5/00 Image enhancement or restoration
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 7/90 Determination of colour characteristics
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• 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
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84
• CPC Class Codes: H04N 9/643 Hue control means, e.g. flesh tone control

Abstract

A transformation rule of color transformation in an appropriate color space is set even without advanced knowledge and know-how. A three-dimensional lookup table unit transforms color information on an input image signal on the basis of a transformation rule. A correction range calculation unit calculates a correction range in a predetermined color space on the basis of a positional relationship between source coordinates and destination coordinates in the color space. A lattice point transfer distance calculation unit calculates the transformation destination coordinates at respective points on the basis of the positional relationship between the source coordinates and the destination coordinates, and a positional relationship between coordinates at the respective points within the correction range and the source coordinates to reflect the calculated transformation destination coordinates on the transformation rule.

Claims

1. An image processing apparatus, comprising:

a transformation unit that transforms color information on an input image signal on the basis of a transformation rule;

a correction range calculation unit that calculates a correction range in a predetermined color space on the basis of a positional relationship between source coordinates and destination coordinates in the color space; and

a point-based transfer distance calculation unit that calculates the transformation destination coordinates at respective points on the basis of the positional relationship between the source coordinates and the destination coordinates, and a positional relationship between coordinates at the respective points within the correction range and the source coordinates to reflect the calculated transformation destination coordinates on the transformation rule.

2. The image processing apparatus according to claim 1,

wherein the point-based transfer distance calculation unit makes the transfer distance at each point smaller as a distance from the source coordinates is larger.

3. The image processing apparatus according to claim 1,

wherein the correction range comprises an oval sphere in which a first line connecting the source coordinates and the destination coordinates is parallel to a long-axis direction.

4. The image processing apparatus according to claim 3,

wherein the correction range calculation unit includes:

a first distance calculation unit that calculates a distance between the source coordinates and the destination coordinates;

a line inclination calculation unit that calculates an inclination of the first line;

a correction range adjustment unit that calculates the coordinate range on the basis of a predetermined adjustment value and the distance calculated by the first distance calculation unit;

a rotation angle calculation unit that calculates a rotation angle by which the coordinate range is rotated, on the basis of the inclination of the first line which is calculated by the line inclination calculation unit; and

a correction range oval sphere expression calculation unit that calculates the oval sphere by rotating the coordinate range calculated by the correction range adjustment unit by the rotation angle.

5. The image processing apparatus according to claim 4,

wherein the correction range calculation unit calculates an inclination Δ

1 of a first cross-section and an inclination Δ

2 of a second cross-section of the first line in the color space by the following expressions (Ex.

     36) and (Ex.

     37) when it is assumed that the source coordinates are O(Ro, Go, Bo), and the destination coordinates are T(Rt, Gt, Bt) in the color space.

6. The image processing apparatus according to claim 5,

wherein the rotation angle calculation unit calculates the rotation angle θ

1 on the first cross-section and the rotation angle θ

2 on the second cross-section in the color space by the following expressions (Ex.

     38) and (Ex.

     39).

7. The image processing apparatus according to claim 3,

wherein the point-based transfer distance calculation unit includes:

a linear expression calculation unit that calculates a linear expression of a second line connecting a first coordinate point included in the correction range and the source coordinates;

an intersection point calculation unit that calculates an intersection point between the oval sphere and the second line on the basis of a mathematical expression of the oval sphere and the linear expression of the second line;

a second distance calculation unit that calculates a distance between the source coordinates and the intersection point;

a third distance calculation unit that calculates a distance between the first coordinate point and the source coordinates;

an influence degree calculation unit that calculates the degree of influence which is the basis of the transfer distance of the first coordinate point according to a ratio of the distance calculated by the second distance calculation unit and the distance calculated by the third distance calculation unit; and

a coordinate calculation unit that calculates the transformation destination coordinates of the first coordinate point on the basis of the degree of influence.

8. The image processing apparatus according to claim 7,

wherein the coordinate calculation unit calculates the transformation destination coordinates of the first coordinate point according to a correction direction (compression direction or parallel direction) designated by the user.

9. The image processing apparatus according to claim 8,

wherein the point-based transfer distance calculation unit includes a transfer characteristic adjustment unit that calculates transfer characteristics adjusted to be increased more than a linear change, and sets the transfer characteristics as a parameter when the coordinate calculation unit calculates the transformation destination coordinates of the first coordinate point.

10. The image processing apparatus according to claim 1,

wherein the coordinates of each point within the correction range to be processed by the point-based transfer distance calculation unit are lattice point coordinates in which all of distances from adjacent points are equal to each other.

11. The image processing apparatus according to claim 1,

wherein the source coordinates and the destination coordinates are input values designated by the user.

12. The image processing apparatus according to claim 1, further comprising a picture adaptation unit that receives, from the user, a type of a memory color correction target, a first preset value of the source coordinates, and a second preset value of the destination coordinates related to each memory color correction target to be corrected, determines whether the memory color correction target designated by the user exists within an image configured by the image signal, or not, analyzes a color distribution of the image, adjusts at least one of the first preset value and the second preset value for each of the correction targets that exist within the image on the basis of analysis results of the color distribution in the image, and sets adjusted values to the source coordinates and the destination coordinates for each of the memory color correction targets.

13. The image processing apparatus according to claim 12,

wherein the picture adaptation unit includes:

a correction target detection unit that detects the presence or absence of an object or a background to be subjected to the memory color correction within the image, and a detection area of the memory color correction target within the image;

a memory color correction determination unit that compares a detection result of the correction target detection unit with the type of the memory color correction target designated by the user to determine the memory color correction target to be conducted;

a histogram generation unit that generates a color space histogram of the image;

a histogram analysis unit that calculates a first analysis result related to a color distribution analysis within the detection area, and a second analysis result related to a color distribution analysis between the color space coordinates indicated by the first preset value and the second preset value, on the basis of the color space histogram; and

a source and destination calculation unit that calculates the source coordinates and the destination coordinates for each of the memory color correction targets which exist within the image, on the basis of the memory color correction target determined by the memory color correction determination unit, the first and second analysis results, and the first and second preset values.

14. The image processing apparatus according to claim 13,

wherein the histogram analysis unit sets main color coordinates indicative of a main color in the detection area as the first analysis result, divides an area between the color space coordinates indicated by the first preset value and the second preset value into a plurality of areas, determines whether a given number of pixels or more exist in the respective areas, or not, in order from an area closer to the first preset value, and sets the existence coordinates which are representative coordinates of the areas in which the given number of pixels or more exist as the second analysis result.

15. The image processing apparatus according to claim 14,

wherein the source and destination calculation unit calculates the source coordinates and the destination coordinates by the following expressions (Ex. 40) and (Ex. 41) assuming that the main color coordinates are OC(OCr, OCg, OCb), the existence coordinates are TE(TEr, TEg, TEb), the first preset value is OP(OPr, OPg, ORb), the second preset value is TP(TPr, TPg, TRb), the source coordinates are O(Ro, Go, Bo), the destination coordinates are T(Rt, Gt, Bt), and following degrees adjustable by the user are F1(0˜

100%) and F2(0˜

100%).

Ro=OPr+(OCr−

OPr)×

F1

Go=OPg+(OCg−

OPg)×

F1

Bo=OPb+(OCb−

OPb)×

F1 

 

(Ex.

     40)

Rt=TPr+(TEr−

TPr)×

F2

Gt=TPg+(TEg−

TEg)×

F2

Rt=TPr+(TEb−

TPb)×

F2 

 

(Ex.

     41)

16. The image processing apparatus according to claim 1,

wherein the correction range calculation unit receives an input of a rule limit number of the transformation rule from the user, compares the number of respective point coordinates within the correction range which is calculated from a size of the correction range with the rule limit number, and recalculates the correction range so that the area range becomes smaller if the rule limit number is smaller than the number of respective dot coordinates within the correction range.

17. The image processing apparatus according to claim 1,

wherein the correction range calculation unit receives an input of a priority order of the memory color correction targets from the user, determines whether the correction ranges of the respective memory color correction targets overlap with each other, and recalculates the correction ranges of the respective memory color correction targets so that a reduction ratio of the correction ranges of the memory color correction targets becomes larger in ascending order of the priority order.

18. The image processing apparatus according to claim 16,

wherein the correction range calculation unit recalculates the correction ranges after at least one of the source coordinates and the destination coordinates is so adjusted as to decrease a distance between the source coordinates and the destination coordinates.

19. The image processing apparatus according to claim 13,

wherein the transformation unit includes at least a first transformation unit and a second transformation unit,

wherein the picture adaptation unit detects the respective display areas of the first color correction target and the second memory color correction target, which are the memory color correction targets designated by the user, within the image,

wherein the correction range calculation unit calculates the respective correction ranges corresponding to the first and second memory color correction targets, and

wherein the point-based transfer distance calculation unit calculates the transformation destination coordinates of the respective points within the correction range of the first memory color correction target to reflect the calculated transformation destination coordinates on the transformation rule of the first transformation unit, and calculates the transformation destination coordinates of the respective points within the correction range of the second memory color correction target to reflect the calculated transformation destination coordinates on the transformation rule of the second transformation unit.

20. The image processing apparatus according to claim 1,

wherein the color space is any one of RGB, HSV, HSU, YUV, HLS, Lab, and YCM.

21. The image processing apparatus according to claim 1,

wherein the transformation rule comprises an LUT (lookup table).

22. An image processing method of transforming color information on an input image signal on the basis of a transformation rule, comprising:

calculating a correction range in a predetermined color space on the basis of a positional relationship between source coordinates and destination coordinates in the color space; and

calculating the transformation destination coordinates at respective points on the basis of the positional relationship between the source coordinates and the destination coordinates, and a positional relationship between coordinates at the respective points within the correction range and the source coordinates to reflect the calculated transformation destination coordinates on the transformation rule.

23. A computer readable recording medium storing a program causing a computer to execute processing comprising:

transforming color information on an input image signal on the basis of a transformation rule;

calculating a correction range in a predetermined color space on the basis of a positional relationship between source coordinates and destination coordinates in the color space; and

calculating the transformation destination coordinates at respective points on the basis of the positional relationship between the source coordinates and the destination coordinates, and a positional relationship between coordinates at the respective points within the correction range and the source coordinates to reflect the calculated transformation destination coordinates on the transformation rule.