Iterative technique for refining color correction look-up tables

Claim 1

A method for refining a color response of a printer, the method comprising: (a) generating a color correction table, the color correction table including a plurality of RGB locations x i , each of the RGB locations x i storing a device RGB value y i , for 1≦i≦N, where N is an integer, the generating including: (a1) printing a color patch corresponding to each of a plurality of device RGB values y j '; (a2) measuring each of the plurality of device RGB values y j ' printed to obtain a corresponding colorimetric RGB location x j '; (a3) calculating a transformation vector t j ' for each of the colorimetric RGB locations x j ', where t j '=y j '-x j ' for 1≦j≦K where K is an integer less than N and storing the transformation vectors into the color correction table at the colorimetric RGB locations x j '; (a4) interpolating the transformation vectors t j ' stored at each of the colorimetric RGB locations x j ' to obtain table transformation vectors t i for other RGB locations of the color correction table, the table transformation vector t i being a weighted sum of the transformation vectors t j ' wherein: ##EQU3## where d ij is a Euclidean distance between a current location and the colorimetric RGB locations x j ', and d t is a predetermined threshold value; (a5) combining each of the table transformation vectors t i with the corresponding RGB location x i to obtain a device RGB value y i of the color correction table, where y i =x i +t i ; and, (b) refining the device RGB values y i of the color correction table, the refining including: (b1) inputting the colorimetric RGB locations x j ' to the color correction table and recovering corresponding device RGB values y i ; (b2) comparing, for each of the colorimetric RGB locations x j ', the device RGB value y j ' printed with the corresponding device RGB value y i recovered to obtain a printer residual error e j ' for each of the colorimetric RGB locations x j '; (b3) interpolating, to other locations in the color correction table, a weighted sum of the printer residual errors e j ' combined with a function of a Euclidean distance d ij between a current table location and the colorimetric RGB locations x j ' to obtain a table residual error e i for each of the RGB locations of the color correction table wherein: ##EQU4## (b4) refining the device RGB values y i of the color correction table by combining the table residual errors e i with the device RGB values y i ; and (b5) repeating steps (b1)-(b4) until the table residual errors e i are within a selected tolerance.

Claim 2

A method for refining a color response of a printer, the method comprising: (a) generating a color correction table, the color correction table including a plurality of RGB locations x i , each of the RGB locations x i storing a device RGB value y i , for 1≦i≦N, where N is an integer, the generating including: (a1) printing a color patch corresponding to each of a plurality of device RGB values y j '; (a2) measuring each of the plurality of device RGB values y j ' printed to obtain a corresponding colorimetric RGB location x j '; (a3) calculating a transformation vector t j ' for each of the colorimetric RGB locations x j ', where t j '=y j '-x j ' for 1≦j≦K where K is an integer less than N and storing the transformation vectors into the color correction table at the colorimetric RGB locations x j '; (a4) interpolating the transformation vectors t j ' stored at each of the colorimetric RGB locations x j ' to obtain table transformation vectors t i for other RGB locations of the color correction table, the table transformation vector t i being a weighted sum of the transformation vectors t j ' wherein: ##EQU3## where d ij is a Euclidean distance between a current location and the colorimetric RGB locations x j ', and d t is a predetermined threshold value; (a5) combining each of the table transformation vectors t i with the corresponding RGB location x i to obtain a device RGB value y i of the color correction table, where y i =x i +t i ; and, (b) refining the device RGB values y i of the color correction table, the refining including: (b1) inputting the colorimetric RGB locations x j ' to the color correction table and recovering corresponding device RGB values y i ; (b2) comparing, for each of the colorimetric RGB locations x j ', the device RGB value y j ' printed with the corresponding device RGB value y i recovered to obtain a printer residual error e j ' for each of the colorimetric RGB locations x j '; (b3) interpolating, to other locations in the color correction table, a weighted sum of the printer residual errors e j ' combined with a function of a Euclidean distance d ij between a current table location and the colorimetric RGB locations x j ' to obtain a table residual error e i for each of the RGB locations of the color correction table wherein: ##EQU4## (b4) refining the device RGB values y i of the color correction table by combining the table residual errors e i with the device RGB values y i ; and (b5) repeating steps (b1)-(b4) until the table residual errors e i are within a selected tolerance.

Claim 3

A method of refining a color correction table of a printer, the color correction table having a plurality of table locations and being generated by printing a plurality of device color values by the printer into a plurality of colorimetric locations and calculating a transformation vector for each of the plurality of colorimetric locations corresponding to the plurality of device color values, the color correction table converting the plurality of colorimetric locations to the plurality of device color values, the method comprising: (a) inputting the plurality of colorimetric locations to the color correction table and recovering a corresponding plurality of table color values; (b) comparing the table color value recovered for the colorimetric location and the device color value corresponding to the colorimetric location to obtain a residual error for each of the plurality of colorimetric locations; (c) interpolating the residual errors to other locations of the color correction table to obtain a table error for each of the plurality of table locations based on a weighted function of the residual errors and a Euclidean distance between the plurality of table locations and the plurality of colorimetric locations; (d) refining the table color values of the color correction table with the table errors calculated for each of the plurality of table locations; and, (e) repeating steps (a)-(d).

Claim 4

A method of refining a color correction table of a printer, the color correction table having a plurality of table locations and being generated by printing a plurality of device color values by the printer into a plurality of colorimetric locations and calculating a transformation vector for each of the plurality of colorimetric locations corresponding to the plurality of device color values, the color correction table converting the plurality of colorimetric locations to the plurality of device color values, the method comprising: (a) inputting the plurality of colorimetric locations to the color correction table and recovering a corresponding plurality of table color values; (b) comparing the table color value recovered for the colorimetric location and the device color value corresponding to the colorimetric location to obtain a residual error for each of the plurality of colorimetric locations; (c) interpolating the residual errors to other locations of the color correction table to obtain a table error for each of the plurality of table locations based on a weighted function of the residual errors and a Euclidean distance between the plurality of table locations and the plurality of colorimetric locations; (d) refining the table color values of the color correction table with the table errors calculated for each of the plurality of table locations; and, (e) repeating steps (a)-(d).

Claim 5

A method of color printing comprising: (a) causing a color printer to print a set of color patches corresponding to a first set of first color space values {Y1}; (b) generating a first set of second color space values {X1} from the set of color patches, such that there is a correspondence between the first sets of first and second color space values {X1}, {Y1}; (c) interpolating the corresponding first and second color space values {X1}, {Y1} to provide a transformation between an enlarged set of first color space values and an enlarged set of second color space values; (d) creating a color correction table from the enlarged set of first color space values and the enlarged set of second color space values, which table provides a transformation between the first and second color spaces; (e) addressing the interpolated color correction table with the first set of second color space values {X1} to retrieve a second set of first color space values {Y2}; (f) comparing the first set of first color space values {Y1} and the second set of first color space values {Y2} to generate a set of error values indicative of a deviation between the first and second sets of first color space values; (g) interpolating the set of error values to generate an enlarged set of error values; (h) modifying the color correction table with the enlarged set of error values; (i) addressing the color correction table with a series of second color space values that represent a picture to retrieve a series of first color space values; and, (j) supplying the series of first color space values to a printer to cause the printer to print the picture.

Claim 6

A method of color printing comprising: (a) causing a color printer to print a set of color patches corresponding to a first set of first color space values {Y1}; (b) generating a first set of second color space values {X1} from the set of color patches, such that there is a correspondence between the first sets of first and second color space values {X1}, {Y1}; (c) interpolating the corresponding first and second color space values {X1}, {Y1} to provide a transformation between an enlarged set of first color space values and an enlarged set of second color space values; (d) creating a color correction table from the enlarged set of first color space values and the enlarged set of second color space values, which table provides a transformation between the first and second color spaces; (e) addressing the interpolated color correction table with the first set of second color space values {X1} to retrieve a second set of first color space values {Y2}; (f) comparing the first set of first color space values {Y1} and the second set of first color space values {Y2} to generate a set of error values indicative of a deviation between the first and second sets of first color space values; (g) interpolating the set of error values to generate an enlarged set of error values; (h) modifying the color correction table with the enlarged set of error values; (i) addressing the color correction table with a series of second color space values that represent a picture to retrieve a series of first color space values; and, (j) supplying the series of first color space values to a printer to cause the printer to print the picture.

Claim 9

A method of color printing comprising: (a) generating a color transformation between a first set of first color space values and a first set of second color space values; (b) interpolating the corresponding first and second color space values to provide the color transformation between an enlarged set of first color space values and an enlarged set of second color space values; (c) creating a color correction table from the enlarged set of first color space values and the enlarged set of second color space values, which table provides a transformation between the first and second color spaces; (d) addressing the interpolated color correction table with the first set of second color space values to retrieve a second set of first color space values; (e) comparing the first set of first color space values and the second set of first color space values to generate a set of error values indicative of a deviation between the first and second sets of first color space values; (f) interpolating the set of error values to generate an enlarged set of error values; (g) modifying the color correction table with the enlarged set of error values; (h) addressing the color correction table with a series of second color space values that represent a picture to retrieve a series of first color space values; and, (i) supplying the series of first color space values to a printer to cause the printer to print the picture; and (j) iteratively repeating steps (d)-(g) until the error values are minimized.

Claim 10

A method of color printing comprising: (a) generating a color transformation between a first set of first color space values and a first set of second color space values; (b) interpolating the corresponding first and second color space values to provide the color transformation between an enlarged set of first color space values and an enlarged set of second color space values; (c) creating a color correction table from the enlarged set of first color space values and the enlarged set of second color space values, which table provides a transformation between the first and second color spaces; (d) addressing the interpolated color correction table with the first set of second color space values to retrieve a second set of first color space values; (e) comparing the first set of first color space values and the second set of first color space values to generate a set of error values indicative of a deviation between the first and second sets of first color space values; (f) interpolating the set of error values to generate an enlarged set of error values; (g) modifying the color correction table with the enlarged set of error values; (h) addressing the color correction table with a series of second color space values that represent a picture to retrieve a series of first color space values; and, (i) supplying the series of first color space values to a printer to cause the printer to print the picture; and (j) iteratively repeating steps (d)-(g) until the error values are minimized.