Image processing apparatus and image processing method as well as computer program

• US 20060098253A1
• Filed: 11/02/2005
• Published: 05/11/2006
• Est. Priority Date: 11/08/2004
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamada, Rui, Masuno, Tomonori, Ohki, Mitsuharu
• Granted Patent: US 7,529,405 B2
• Time in Patent Office: Days
• US Class Current: 358/518
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence
• CPC Class Codes: H04N 25/611 Correction of chromatic aberration

Abstract

An image processing apparatus and an image processing method are disclosed by which an image correction process for a false color such as a purple fringe can be executed efficiently while excessive reduction of the saturation is prevented to produce image data of a high quality. A saturation reduction rate corresponding to each pixel is calculated, and saturation reduction of the pixel is executed based on the saturation reduction rate. Then, saturation correction is executed so that the difference between the hue of the pixel whose saturation has been reduced and a surrounding reference pixel may be reduced. Further, a surrounding pixel to be referred to in the saturation correction process is selected along a scanning line.

Claims

1. An image processing apparatus, comprising:

a correction parameter calculation section for calculating, as a correction parameter for component pixels of a processing image, a saturation reduction rate corresponding to each of the pixels; and

a correction processing section for applying the saturation reduction rate to execute a pixel value correction process including a saturation reduction process of the component pixels of the processing image;

said correction processing section including a pixel saturation reduction processing section for executing the saturation reduction process for each of the pixels based on the saturation reduction rate calculated by said correction parameter calculation section, and a pixel saturation correction processing section for correcting the saturation of any saturation reduction pixel whose saturation has been reduced by said pixel saturation reduction processing section so that the difference of the saturation of the saturation reduction pixel and the saturation of a surrounding reference pixel is reduced.

2. The image processing apparatus according to claim 1, wherein said correction processing section further includes a blurring processing section for executing, for output data of said pixel saturation correction processing section, a blurring process of reducing the difference in hue between any pixel for which the saturation reduction process has been performed and a surrounding pixel.

3. The image processing apparatus according to claim 1, wherein said pixel saturation correction processing section selects one of those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as a reference pixel and executes the saturation correction process for the saturation reduction pixel so that the difference between the saturation of the selected reference pixel and the saturation of the saturation reduction pixel is reduced.

4. The image processing apparatus according to claim 1, wherein said pixel saturation correction processing section selects those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as reference pixels and executes a process of adjusting the saturation of the saturation reduction pixel so as to approach the saturation of that one of the reference pixels which has the highest saturation.

5. The image processing apparatus according to claim 1, wherein said pixel saturation correction processing section selects those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as reference pixels and executes, if the saturation of that one of the reference pixels which has the highest saturation is equal to or lower than the saturation of the saturation reduction pixel prior to the saturation reduction, a process of adjusting the saturation of the saturation reduction pixel so as to approach the saturation of the saturation reduction pixel prior to the saturation reduction.

6. The image processing apparatus according to claim 1, wherein said correction parameter calculation section calculates, as regards a noticed pixel selected from within the processing image,

(a) a purple degree as similarity information between the hue of the noticed pixel and the hue of a false color, and

(b) distance information of the noticed pixel from an overexposed highlight pixel, calculates

(c) a false color degree based on the purple degree and the distance information, and

(d) a directional gain based on direction information of the noticed pixel from the overexposed highlight pixel, and

calculates the saturation reduction rate corresponding to the noticed pixel based on the false color degree and the directional gain.

7. The image processing apparatus according to claim 6, wherein said correction parameter calculation section

calculates the false color degree which has a value which increases as the similarity between the hue of the noticed pixel and the hue of the false color increases and as the distance from the overexposed highlight pixel increases,

calculates the directional gain which has a value which increases as the parallelism between the noticed pixel and overexposed highlight pixel and the scanning line increases, and

calculates the saturation reduction rate which has a value which increases as the false color degree of the noticed pixel increases and as the directional gain increases, and

said pixel saturation reduction processing section executes the saturation reduction process for each pixel based on the saturation reduction rate calculated by said correction parameter calculation section.

8. The image processing apparatus according to claim 6, wherein the false color is a purple fringe, and the purple degree serves as the similarity information between the hue of the noticed pixel and the hue of the purple fringe.

9. An image processing method, comprising the steps of:

calculating, as a correction parameter for component pixels of a processing image, a saturation reduction rate corresponding to each of the pixels; and

applying the saturation reduction rate to execute a pixel value correction process including a saturation reduction process of the component pixels of the processing image;

the correction processing step including steps of executing the saturation reduction process for each of the pixels based on the saturation reduction rate calculated by the correction parameter calculation step, and correcting the saturation of any saturation reduction pixel whose saturation has been reduced by the pixel saturation reduction processing step so that the difference of the saturation of the saturation reduction pixel and the saturation of a surrounding reference pixel is reduced.

10. The image processing method according to claim 9, wherein the correction processing step further includes a blurring processing step of executing, for output data of the pixel saturation correction processing step, a blurring process of reducing the difference in hue between any pixel for which the saturation reduction process has been performed and a surrounding pixel.

11. The image processing method according to claim 9, wherein the pixel saturation correction processing step selects one of those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as a reference pixel and executes the saturation correction process for the saturation reduction pixel so that the difference between the saturation of the selected reference pixel and the saturation of the saturation reduction pixel is reduced.

12. The image processing method according to claim 9, wherein the pixel saturation correction processing step selects those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as reference pixels and executes a process of adjusting the saturation of the saturation reduction pixel so as to approach the saturation of that one of the reference pixels which has the highest saturation.

13. The image processing method according to claim 9, wherein the pixel saturation correction processing step selects those pixels which are positioned in the proximity of the saturation reduction pixel and along the same scanning line as that of the saturation reduction pixel as reference pixels and executes, if the saturation of that one of the reference pixels which has the highest saturation is equal to or lower than the saturation of the saturation reduction pixel prior to the saturation reduction, a process of adjusting the saturation of the saturation reduction pixel so as to approach the saturation of the saturation reduction pixel prior to the saturation reduction.

14. The image processing method according to claim 9, wherein the correction parameter calculation step calculates, as regards a noticed pixel selected from within the processing image,

(a) a purple degree as similarity information between the hue of the noticed pixel and the hue of a false color, and

(b) distance information of the noticed pixel from an overexposed highlight pixel,

calculates

(c) a false color degree based on the purple degree and the distance information, and

(d) a directional gain based on direction information of the noticed pixel from the overexposed highlight pixel, and

calculates the saturation reduction rate corresponding to the noticed pixel based on the false color degree and the directional gain.

15. The image processing method according to claim 14, wherein the correction parameter calculation step

calculates the false color degree which has a value which increases as the similarity between the hue of the noticed pixel and the hue of the false color increases and as the distance from the overexposed highlight pixel increases,

calculates the directional gain which has a value which increases as the parallelism between the noticed pixel and overexposed highlight pixel and the scanning line increases, and

calculates the saturation reduction rate which has a value which increases as the false color degree of the noticed pixel increases and as the directional gain increases, and

said pixel saturation reduction processing step executes the saturation reduction process for each pixel based on the saturation reduction rate calculated by the correction parameter calculation step.

16. The image processing method according to claim 14, wherein the false color is a purple fringe, and the purple degree serves as the similarity information between the hue of the noticed pixel and the hue of the purple fringe.

17. A computer program for causing image processing to be executed on a computer, comprising the steps of:

calculating, as a correction parameter for component pixels of a processing image, a saturation reduction rate corresponding to each of the pixels; and

applying the saturation reduction rate to execute a pixel value correction process including a saturation reduction process of the component pixels of the processing image;

the correction processing step including steps of executing the saturation reduction process for each of the pixels based on the saturation reduction rate calculated by the correction parameter calculation step, and correcting the saturation of any saturation reduction pixel whose saturation has been reduced by the pixel saturation reduction processing step so that the difference of the saturation of the saturation reduction pixel and the saturation of a surrounding reference pixel.