System and method for image processing by automatic color dropout

• US 6,757,426 B2
• Filed: 03/21/2001
• Issued: 06/29/2004
• Est. Priority Date: 03/21/2001
• Status: Active Grant

• Current Assignee: Kodak Alaris Inc (KPP (no. 2) Trustees Ltd.)
• Original Assignee: Eastman Kodak Company
• Inventors: Lee, Yongchun, Alescio, John J., Zhou, Wenjin, Link, Bruce A.
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): Alavi, Amir
• Application Number:
  US09/813,481
• Publication Number:
  US 20020136447A1
• Time in Patent Office: 1,196 Days
• Field of Search: 382/162, 382/163, 382/165, 382/168, 382/169, 382/170, 382/172, 382/276, 358/449, 358/473, 358/488, 358/500, 358/501, 358/505, 358/522, 358/523, 358/530
• US Class Current: 382/163
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths

Abstract

An automatic method for processing a color form includes: a) scanning the color form in color space, forming a digital color image, and converting the digital color image into a two-dimensional binary image in chrominance space; and b) conducting a color form dropout process. Also, an automatic color dropout system includes: 1) a color detection system, including means for: (1a) scanning a color document and providing a digital image; (1b) converting the color digital image into luminance-chrominance space; (1c) detecting a background gray level, and assigning it to a Background Value; (1d) measuring color distribution; (1e) detecting the colors present; (1f) generating a color dropout table for each color; and 2) a color dropout system, including means for: (2a) scanning a color form document and providing a digital image; (2b) converting the digital image into luminance-chrominance space; (2c/d) storing and accessing the color dropout table; (2e) applying a color dropout map to the digital image; and (2f) replacing a pixel value with the Background Value.

Claims

1. An automatic method for processing a color form, the method comprising the step of:

a) detecting color in a color form sample, comprising the steps of;

(a1) scanning the color form sample and producing digital image records;

(a2) converting the digital image records into a luminance image record and two chrominance image records in a luminance-chrominance color space;

(a3) detecting background gray levels for the luminance image record from step (a2) and assigning it to a Background Value;

(a4) applying a global threshold level input to the output of step (a2) to obtain a binary image;

(a5) measuring color distribution with the output of steps (a4) and (a2);

(a6) detecting colors and distributions in the color form sample using the output of step (a5);

(a7) generating color tables with the output of step (a6); and

(a8) merging a dropout color table with the output of step (a7); and

b) conducting a color dropout process.

2. A method according to claim 1 wherein step b) conducting the color dropout process, comprises the steps of:

(b1) scanning a color form document and producing a digital image in the form of a stream of color image pixels;

(b2) converting the output from the scanner of step (b1) into a luminance channel and two chrominance channels;

(b3) reading color data from the two chrominance channels;

(b4) loading to a color look-up table;

(b5) replacing luminance value in the digital image by a Background Value; and

wherein information from the color dropout table of step (a8) is loaded to the color look-up table of step (b4).

3. A method according to claim 2 wherein the steps of (b2) through (b5) are repeated for each color pixel within the scanned image.

4. A method according to claim 3 further comprising the step of (b6):

applying a threshold function and producing a color dropout bitmap image.

5. A method according to claim 3 wherein the Background Value from step (a3) is used as the replacement grayscale value of step (b5), which represents the color pixel to be removed.

6. A method according to claim 2 wherein a red, green and blue digital image is produced in step (b1), output from the scanner is converted into two chrominance channels, Cb for blue chrominance, and Cr for red chrominance, and one luminance channel, Y in step (b2), and color data is read from the two chrominance channels, Cb and Cr, in step (b3).

7. An automatic method for processing a color image, the method comprising the steps of:

a) detecting color in a color form by scanning the color form in color space, forming a digital color image, and converting the digital color image to a two-dimensional binary image in chrominance space;

b) conducting a color form dropout process dropping out the color or colors determined in step a); and

wherein step b) comprises the step of;

replacing grayscale values of color pixels by a Background Value.

8. An automatic method for processing a color image, the method comprising the steps of:

a) detecting color in a color form by scanning the color form in color space, forming a digital color image, and converting the digital color image to a two-dimensional binary image in chrominance space;

b) conducting a color form dropout process dropping out the color or colors determined in step a);

wherein step a) comprises the steps of;

(a1) Scanning a color form sample in color, and forming digital image records;

(a2) Converting the digital image records into a luminance image record and two chrominance image records in a luminance-chrominance color space;

(a3) Detecting the background level in the luminance image record, and assigning to it a Background Value;

(a4) Applying the Background Value to the luminance image record and producing a binary image;

(a5) Measuring color distribution for non-background pixels in the binary image;

(a6) Detecting the number of colors and color distributions;

(a7) Converting each color distribution map into a color table; and

(a8) Selecting a dropout color table for use in the color dropout process.

9. A method according to claim 8 wherein step b) comprises the steps of:

(b

     1) Scanning a color form to produce a stream of color image pixels;

(b2) Converting the incoming color signals of an image pixel into luminance-chrominance signals;

(b3) Taking the chrominance signals, or luminance-chrominance signals, of each of the image pixels as input for a look-up table, and returning with a “

0”

or “

1”

; and

(b4) Replacing the luminance value of the corresponding image pixel by the Background Value, if the return value of the look-up table is “

1”

.

10. A method according to claim 9 wherein steps (b2) through (b4) are repeated for each color pixel within the digital image to produce a color dropout binary image.

11. A method according to claim 10 wherein scanning is step (b1) is to produce a stream of color pixels and grayscale image pixels.

12. A method according to claim 11 further comprising the step of replacing the grayscale image pixels with the Background Value.

13. A method according to claim 12 further comprising the step of turning grayscale value, or Background Value, of the image pixel into “

0”

(Black) or “

1”

(White).

14. An image processing system for automatic color dropout, the system comprising:

1) a color detection system, comprising;

(1a) a color scanner for scanning a color document and providing a digital image;

(1b) a means for converting color the digital image into luminance-chrominance space;

(1c) a means for detecting a background gray level, and assigning to it a Background Value;

(1d) a means for measuring color distribution;

(1e) a means for detecting the number of colors and their distributions;

(1f) a means for generating a color dropout table for each color present; and

2) a color dropout system.

15. An image processing system according to claim 14 wherein the color dropout system comprises:

(2a) a color scanner for scanning a color form document and providing a digital image;

(2b) a means for converting the digital image into luminance-chrominance space;

(2c) a means for storing the color dropout table;

(2d) a means for accessing the color dropout table;

(2e) a means for applying a color dropout map to the digital image; and

(2f) a means for replacing a pixel value with the Background Value based on the color dropout table.

16. An image processing system according to claim 15 wherein a third dimension is incorporated into the color dropout table, which is in luminance-chrominance space.

17. An image processing system according to claim 15 wherein the digital image comprises grayscale, and color conversion or grayscale.

18. An image processing system according to claim 17 wherein step (1c) comprises the step of replacing grayscale pixels that contain the color to be dropped by a Background Value.

19. An image processing system according to claim 18 further comprising a means for applying an adaptive image thresholding process (ATP) to produce a binary image.

20. An image processing system according to claim 19 further comprising a final noise filter.