Shading noise filter
View Patent ↗A shading correction is employed for a scanner to correct shading distortion. However, an image corrected with the shading corrective curve has shading noise lines due to the effects of various factors in the producing process of the shading corrective curve. The characteristic of the shading noise is that the each value of any primary color channel, of each pixel in a line is higher or lower than of the adjacent two pixels in other lines, wherein a color channel is one of red, green, or blue channel. Hence, the quality of the image is improved by removing the shading noise detected from the characteristic described above.
1. A method for eliminating shading noise, comprising:
detecting one or more shading noise lines of a shading noise in an image based on two adjacent lines;
eliminating said shading noise from said one or more shading noise lines in said image;
wherein said detecting one or more shading noise lines comprises detecting one or more shading noise lines by a characteristic of said shading noise; and
wherein a detecting function of said shading noise is: [X(i−1,j)−X(i,j)][X(i,j)−X(i+1,j)]<0, wherein X(i,j) comprises one color value in a coordinate (i,j) of an image, and wherein X(i−1,j) and X(i+1,j) comprise color values of same said color as X(i,j).
2. The method for eliminating shading noise according to claim 1 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line higher than adjacent two pixels in said two adjacent lines.
3. The method for eliminating shading noise according to claim 1 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line higher a certain percent than adjacent two pixels in said two adjacent lines.
4. The method for eliminating shading noise according to claim 1 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line lower than adjacent two pixels in said two adjacent lines.
5. The method for eliminating shading noise according to claim 1 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line lower a certain percent than adjacent two pixels in said two adjacent lines.
6. The method for eliminating shading noise according to claim 1 , wherein a line in said image has shading noise if a detecting result of said detecting function is true over a certain percent.
7. The method for eliminating shading noise according to claim 6 , wherein said certain percent comprises 80 percent.
8. The method for eliminating shading noise according to claim 2 , wherein said color value is red, green, or blue.
9. The method for eliminating shading noise according to claim 3 , wherein said color value is red, green, or blue.
10. The method for eliminating shading noise according to claim 1 , wherein said shading noises are detected by multiplying a first difference with a second difference, wherein the first difference is taken between a color value of a first adjacent pixel and a color value of a given pixel, and wherein the second difference is taken between a color value of a second adjacent pixel and said color value of said given pixel.
11. The method for eliminating shading noise according to claim 10 , wherein a new color value of said given pixel comprises an average of said color value of said first adjacent pixel and said color value of said second adjacent pixel for eliminating said shading noise.
12. The method for eliminating shading noise according to claim 10 , wherein said color value of said given pixel is not transformed if detecting shading noise is false.
13. A method for eliminating shading noises, comprising:
detecting a shading noise in an image by multiplying a first difference with a second difference, wherein the first difference is taken between color values of a first adjacent pixel and a color value of a given pixel, and wherein the second difference is taken between a color value of a second adjacent pixel and said color value of said given pixel;
determining one or more shading noise lines; and eliminating said shading noise from said one or more shading noise lines in said image; and
wherein a detecting function of said shading noise is: [X(i−1,j)−X(i,j)][X(i,j)−X(i+1,j)]<0, wherein X(i,j) comprises one color value in a coordinate (i,j) of an image, and wherein X(i−1,j) and X(i+1,j) comprise color values of same said color as X(i,j).
14. The method for eliminating shading noise according to claim 13 , wherein a line in said image has shading noise if a detecting result of said detecting function is true over a certain percent.
15. The method for eliminating shading noise according to claim 14 , wherein said certain percent comprises 80 percent.
16. The method for eliminating shading noise according to claim 13 , wherein a new color value of said given pixel comprises an average of said color value of said first adjacent pixel and said color value of said second adjacent pixel for eliminating said shading noise.
17. The method for eliminating shading noise according to claim 13 , wherein said color value of said given pixel is not transformed if detecting shading noise is false.
18. An apparatus, comprising:
means for detecting one or more shading noise lines of a shading noise in an image based on two adjacent lines;
means for eliminating said shading noise from said one or more shading noise lines in said image;
wherein said means for detecting one or more shading noise lines comprises means for detecting one or more shading noise lines by a characteristic of said shading noise; and
wherein said means for detecting one or more shading noise lines comprises a detecting function of said shading noise comprising: [X(i−1,j)−X(i,j)][X(i,j)−X(i+1,j)]<0 wherein X(i,j) comprises one color value in a coordinate (i,j) of an image; X(i−1,j) and X(i+1,j) comprise color values of same said color.
19. The apparatus of claim 18 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line higher than adjacent two pixels in said two adjacent lines.
20. The apparatus of claim 18 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line higher a certain percent than adjacent two pixels in said two adjacent lines.
21. The apparatus of claim 18 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line lower than adjacent two pixels in said two adjacent lines.
22. The apparatus of claim 18 , wherein said characteristic comprises a line with one pixel width and at least one color value of one color in said shading noise line lower a certain percent than adjacent two pixels in said two adjacent lines.
23. The apparatus of claim 18 , wherein a line in said image has shading noise if a detecting result of said detecting function is true over a certain percent.
24. The apparatus of claim 23 , wherein said certain percent comprises 80 percent.
25. The apparatus of claim 18 , wherein said means for detecting one or more shading noise lines comprises means for detecting one or more shading noise lines by multiplying a first difference with a second difference, wherein the first difference is taken between a color value of a first adjacent pixel and a color value of a given pixel, and wherein the second difference is taken between a color value of a second adjacent pixel and said color value of said given pixel.
26. The apparatus of claim 18 , wherein a new color value of said given pixel comprises an average of said color value of said first adjacent pixel and said color value of said second adjacent pixel for eliminating said shading noise.
27. The apparatus of claim 25 , wherein said color value of said given pixel is not transformed if detecting shading noise is false.
28. An apparatus, comprising:
a scanner, said scanner capable of:
detecting a shading noise in an image by multiplying a first difference with a second difference, wherein the first difference is taken between color values of a first adjacent pixel and a color value of a given pixel, and wherein the second difference is taken between a color value of a second adjacent pixel and said color value of said given pixel;
determining one or more shading noise lines; and eliminating said shading noise from said one or more shading noise lines in said image; and
wherein said scanner is further capable of detecting a shading noise by a detecting function of said shading noise comprising: [X(i−1,j)−X(i,j)][X(i,j)−X(i+1,j)]<0 wherein X(i,j) comprises one color value in a coordinate (i,j) of an image; X(i−1,j) and X(i+1,j) comprise color values of same said color.
29. The apparatus of claim 28 , wherein a line in said image has shading noise if a detecting result of said detecting function is true over, a certain percent.
30. The apparatus of claim 29 , wherein said certain percent comprises 80 percent.
31. The apparatus of claim 28 , wherein a new color value of said given pixel comprises an average of said color value of said first adjacent pixel and said color value of said second adjacent pixel for eliminating said shading noise.
32. The apparatus of claim 28 , wherein said color value of said given pixel is not transformed if detecting shading noise is false.