Automated image calibration

Claim 2

The method of claim 1, wherein said input capture device (224) comprises a scanner having a scanner bed, and wherein said calibration image comprises: registration means (502) for determining a location of a printed calibration image on said scanner bed; storage means (506) for recording information regarding a print path calibration associated with said calibration image; dotgain means (510) for compensating for dotgain in said printed calibration image; noise reduction means (512) for reducing noise in said printed calibration image; and tracking means (504) for identifying boundaries in said calibration image.

Claim 3

The method of claim 2, wherein said calibration image further comprises a color block (508) having a multitude of colors, and wherein the step (412) of measuring distortions in said calibration image caused by said processing comprises the step of creating (704) a lookup table (1002, 1004) having entries for said colors in said color block, wherein said entries are associated with original colors and response colors, and wherein said original colors represent said colors in said color block.

Claim 4

The method of claim 3, wherein the step (412) of calculating calibration coefficients for offsetting said distortions comprises the steps of: (1) creating (803) a compensation table (1008) having entries associated with desired colors; (2) selecting one of said entries; (3) using (810,812,814,816,818) said original and response colors for determining a stimulus color for said desired color associated with said selected entry; (4) saving (824) said stimulus color in said selected entry; and (5) repeating steps (1)-(4) for each of said entries.

Claim 5

The method of claim 4, wherein said step for using said original and response colors for determining a stimulus color for said desired color associated with said selected entry comprises the steps of: (i) clearing (810) a stimulus accumulator; (ii) initializing (810) an error; (iii) generating (812) a mixed color by adding said error to said desired color; (iv) determining (812) a closest color to said mixed color among said response colors; (v) identifying (814) one of said original colors associated with said closest color; (vi) adding (814) said identified original color with values in said stimulus accumulator; (vii) updating (816) said error by determining a difference between said desired color and closest color; (viii) updating (812) said mixed color by adding said error to said desired color; (ix) updating (812) said closest color by determining which of said response colors is closest to said mixed color; and (x) repeating steps(v)-(ix) for a finite number of iterations such that said stimulus accumulator converges upon said stimulus color.

Claim 6

The method of claim 4, wherein the step of precompensating the image of the original document by modifying the image according to said calibration coefficients comprises the steps of: (i) receiving (906) a pixel color associated with a pixel, wherein said pixel color has a multitude of color bits; (ii) retrieving (916) one of said stimulus colors in said compensation table from a position identified by said color bits; (iii) retrieving (916) adjacent stimulus colors from said compensation table; (iv) generating (916) a high resolution stimulus color by using all of said color bits to interpolate between said retrieved stimulus color and said adjacent stimulus color; (v) replacing (910) said pixel color with said high resolution stimulus color; and (vi) repeating steps (i)-(v) for all pixels in the image.

Claim 7

The method of claim 2, wherein said calibration image further comprises a grayscale block having a multitude of grays, and wherein the step of measuring distortions in said calibration image caused by said processing comprises the step of creating a lookup table (1402, 1404, 1406) having entries for said grays, wherein each of said entries is associated with a desired or stimulus gray and a response gray.

Claim 8

The method of of claim 7, wherein the step of calculating calibration coefficients for offsetting said distortions comprises the steps of: (1) selecting one of said entries; (2) for said desired gray associated with said selected entry, identifying (1216) a closest gray among said response grays in any of said entries; (3) saving (1218) said stimulus gray associated with said closest gray in a compensation table at a position indexed by said desired gray associated with said selected entry; and (4) repeating steps (1)-(3) for each of said entries.

Claim 9

The method of claim 8, wherein the step of precompensating the image of the original document by modifying the image according to said calibration coefficients comprises the steps of: (1) selecting (1308) a gray in the image; (2) retrieving (1308) one of said stimulus grays in said compensation table from a position indexed by said selected gray; (3) replacing (1308) said selected gray with said retrieved stimulus gray in said image; and (4) repeating steps (1)-(3) for all grays in the image.

Claim 10

A document processing system comprising: (1) a print path comprising: (a) image capture means (224) for capturing an image of an original document; (b) means for controlling (202) said image capture means; (c) one or more application programs (206); (d) printing means (226) for generating a printed document having said image; (e) means (228) for controlling said printing means; (2) means for automatically calibrating the print path such that said printed document has a true representation of said image, said means for automatically calibrating comprising: (a) means (404) for generating calibration coefficients for offsetting distortions caused by said print path; and (b) means (416) for precompensating said image of said original document by modifying said image according to said calibration coefficients.