Color image enhancement
View Patent ↗A color image is enhanced in the following fashion. A saturation detector (SDT) detects a degree of color saturation (LC, CC) that occurs in an image area (SP). A filter arrangement (DE 1 , DE 2 , DE 3 ) filters at least one spatial detail in the image area to a degree that depends on the degree of color saturation. This allows an improvement of perceptual quality of color images.
1. A method of image enhancement, comprising:
detecting a degree of color saturation in an image area; and
filtering at least one spatial detail in the image area by:
determining a first luminance value corresponding to a pixel of interest in the image area;
determining a second luminance value corresponding to one or more neighboring pixels neighboring the pixel of interest;
obtaining a difference in luminance value between the first luminance value and the second luminance value; and
amplifying the difference in luminance value by a factor that increases as the degree of color saturation increases.
2. A method according to claim 1 , further comprising:
determining a first a chrominance value corresponding to the pixel of interest in the image area;
determining a second chrominance value corresponding to the one or more neighboring pixels neighboring the pixel of interest; and
obtaining a difference in chrominance value between the first chrominance value and the second chrominance value.
3. A method according to claim 2 , wherein the difference in chrominance value is amplified.
4. A method according to claim 3 , wherein, in the filtering step, the factor to which a difference in chrominance value is amplified is greater than the factor to which a difference in luminance value is amplified.
5. A method according to claim 1 , wherein, the degree of color saturation that is detected is that of the pixel of interest.
6. A method according to claim 5 , further comprising:
a center deviation detection sub-step in which an absolute difference is determined between a chrominance value that belongs to the pixel of interest and a central value, which corresponds with an insignificant degree of saturation; and
a control value generation sub-step in which a control value is generated on the basis of the absolute difference, the control value determining the degree to which the difference in value between the pixel of interest and the neighboring pixels is amplified.
7. A method according to claim 1 , wherein the filtering step further comprises:
a typical value calculation sub-step in which a typical value of the neighboring pixels is determined;
a subtraction sub-step in which the typical value is subtracted from a value that belongs to the pixel of interest, so as to obtain the difference in value as being a difference in value between the pixel of interest and the typical value;
a multiplication sub-step in which the difference in value between the pixel of interest and the typical value is multiplied by the factor, so as to obtain an amplified difference value; and
an adding sub-step in which the typical value is added to the amplified difference value, so as to obtain a modified value for the pixel of interest.
8. A method according to claim 1 , comprising:
a sequencing step in which respective pixels in a color image are successively designated, one by one, as the pixel of interest.
9. A method according to claim 1 , comprising:
a pixel selection step in which a set of pixels is formed, which includes the pixel of interest, on the basis of a predefined aperture, the difference in value being established on the basis of the set of pixels.
10. An image enhancer system, comprising:
a saturation detector to detect a degree of color saturation that occurs in an image area;
a filter arrangement to filter at least one spatial detail in the image area according to:
a first value corresponding to a pixel of interest in the image area;
a second value corresponding to one or more neighboring pixels neighboring the pixel of interest, and
a difference in value between the first value and the second value, the difference in value amplified by a factor that increases linearly as the degree of color saturation increases starting from zero color saturation.
11. The image enhancer system of claim 10 , further comprising a display device coupled to the saturation detector and the filter arrangement configured to display an enhanced color image.
12. An image enhancer system, comprising:
a saturation detector to detect a degree of color saturation that occurs in an image area;
a filter arrangement to filter at least one spatial detail in the image area according to:
a first chrominance value corresponding to a pixel of interest in the image area;
a second chrominance value corresponding to one or more neighboring pixels neighboring the pixel of interest;
a difference in chrominance value between the first chrominance value and the second chrominance value; and
an amplification of the difference in chrominance value by a factor that decreases as the degree of color saturation increases.
13. The image enhancer system of claim 12 , further comprising:
determining a first a luminance value corresponding to the pixel of interest in the image area;
determining a second luminance value corresponding to the one or more neighboring pixels neighboring the pixel of interest; and
obtaining a difference in luminance value between the first luminance value and the second luminance value.
14. An image enhancer system, comprising:
a saturation detector to detect a degree of color saturation that occurs in an image area; and
a filter arrangement to filter at least one spatial detail in the image area according to:
a first luminance value corresponding to a pixel of interest in the image area;
a second luminance value corresponding to one or more neighboring pixels neighboring the pixel of interest;
a difference in luminance value between the first value and the second value; and
an amplification of the difference in luminance value by a factor that increases as the degree of color saturation increases.
15. The image enhancer system of claim 14 , wherein the difference in chrominance value is amplified.
16. A method of image enhancement, comprising:
detecting a degree of color saturation in an image area; and
filtering at least one spatial detail in the image area by:
determining a first value corresponding to a pixel of interest in the image area, wherein the first value is at least one of: a first luminance value or a first chrominance value;
determining a second value corresponding to one or more neighboring pixels neighboring the pixel of interest, wherein the second value is at least one of: a second luminance value or a second chrominance value and
obtaining a difference in value between the first value and the second value, the difference in value amplified by a factor that increases linearly as the degree of color saturation increases starting from zero color saturation.
17. A method according to claim 16 , wherein the difference in value that is amplified includes at least one of: a difference in luminance value or a difference in chrominance value.
18. A method of image enhancement, comprising:
detecting a degree of color saturation in an image area; and
filtering at least one spatial detail in the image area by:
determining a first value corresponding to a pixel of interest in the image area;
determining a second value corresponding to one or more neighboring pixels neighboring the pixel of interest;
obtaining a difference in value between the first value and the second value; and
amplifying the difference in value by a factor that decreases as the degree of color saturation increases, wherein the difference in value that is amplified includes a chrominance value.
19. A method according to claim 18 , wherein, in the filtering step, the difference in value that is amplified comprises a luminance value.