Computerized memory mapping method for transforming color data

• US 5,732,151 A
• Filed: 07/10/1997
• Issued: 03/24/1998
• Est. Priority Date: 03/03/1995
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Wall, Shane D., Moon, Eva-Maria, Pritchard, Thomas B.
• Primary Examiner(s): COUSO, YON JUNG
• Application Number:
  US08/891,248
• Time in Patent Office: 257 Days
• Field of Search: 382/167, 382/162, 382/276, 358/519, 358/520, 358/521, 358/522, 358/523, 358/457, 358/518
• US Class Current: 382/167
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening
• CPC Class Codes: H04N 1/6019 using look-up tables H04N1/6025 takes precedence

Abstract

A method adapted for implementation in a computer system for correcting and half toning color data in a list of colors is provided. Starting with the first color in the list, color corrections are performed. Using traditional half toning methods, descriptions of the resulting printable dots for each position in the halftone matrix for that color are determined. Color corrections and half toning are repeated for each of the colors in the list. A lookup table is compiled. As each pixel of the image from which the list of colors was compiled is encountered, the printable dots are determined by reference to the lookup table.

Claims

1. A computerized memory mapping method for transforming color data representative of an image from a predetermined color pixel data set for said image generated by a first device and for displaying the image with a second device using transformed color data, said second device having a range of output threshold signal abilities, comprising the steps of:

receiving said predetermined color pixel data set as a first color space construct data set for said image to be displayed;

correcting said predetermined color pixel data set for device-dependent variables;

transforming corrected predetermined color pixel data set from said first color space construct data set into a second device color pixel data set for a second color space construct inherent to said second device;

for each output threshold signal ability of said second device and the predetermined color pixel data set for said image by said first device, determining each output signal to be generated for each primary color in each said color in said second device color pixel data set;

storing each said output signal second device color pixel data set as a separate matrix of cells of indexed output signal values for each said color in said second device color pixel data set such that each cell of each matrix is indexed to a corresponding single data point of said predetermined color pixel data set; and

for each pixel of said image,

selecting the separate matrix of indexed output signals corresponding to a data point of said predetermined color pixel data set for said pixel of said image,

determining which output threshold signal is to be generated corresponding to the data point value of said predetermined color pixel data set for said pixel of said image,

selecting the cell of the selected matrix based upon said output threshold signal to be generated,

sending from said selected cell the indexed output signal value for each said second color space construct stored therein, and

displaying a pixel color of said second device color pixel set corresponding to said indexed output signal value.

2. The method as set forth in claim 1, following said step of correcting said predetermined set of pixel data for device-dependent variables of said second device, comprising the further steps of:

determining whether the color space construct of said second device is different from said color space construct of said first device; and

skipping said step of transforming said color pixel data from said first color space construct into a second device color space construct when said first color space construct and said second color construct are not different.

3. The method as set forth in claim 1, where said second device color pixel data set comprises:

data point values for cyan, magenta, yellow primary colors are used for a color printing device.

4. A computer memory device instruction set implementing a method for printing a color hard copy of an image, defined as a predetermined set of data points of pixel data generated by a first apparatus that processes color data using a first color space construct, using a second apparatus that processes color data using a second color space construct and a dithering matrix having a predetermined number of cells with each cell containing a threshold value to provide a threshold pattern for an entire image in the dither method of image printing and having predetermined device dependent color correction variables correlated to said first color space construct and said second color space construct, said method comprising the steps of:

correcting each said primary color data point in said first table in accordance with each of said color correction variables to create a table of corrected primary color data points;

determining if said first color space construct and said second color space construct are identical, and

if identical, continuing said method by selecting and using said table of corrected primary color data points, or

if not identical, transforming each said corrected primary color data point from said first color space construct into a corrected primary color data point in said second color space construct to create a table of second color space corrected primary color data points and continuing said method by selecting and using said table of second color space corrected primary color data points;

for each threshold value of said dither matrix and each corrected primary color data point of the selected table,

determining each output signal needed for each said primary color in said selected table, and

storing each said output signal needed as a separate matrix of cells, having the same structure as said dither matrix, of output signal for each primary color in said selected table such that each cell of all matrices is indexed to a corresponding single primary color data point of said predetermined set of primary color data points for each pixel of said image from said first apparatus; and

printing said image pixel-by-pixel by

selecting the separate matrix of cells indicated for the first pixel single primary color data point of said predetermined set of primary color data points,

determining which cell of said dither matrix corresponds to said first pixel single primary color data point of said predetermined set of primary color data points,

selecting the cell of the separate matrix of cells indicated for the first pixel single primary color data point of said predetermined set of primary color data points based upon said determined cell of said dither matrix,

sending the data point of the selected cell of the separate matrix of cells indicated for the first pixel single primary color data point of said predetermined set of primary color data points as an output signal, and

printing a color of said selected table corresponding to said selected cell of the separate matrix of cells indicated for the first pixel single primary color data point of said predetermined set of primary color data points based upon said output signal.

5. The method as set forth in claim 4, further comprising:

repeating said steps for printing said image for each primary color data point.

6. A method for printing a color image, generated on an origin device and represented by data triplet values for each pixel of said color image, with a printer device using a printer device color space data construct, comprising the steps of:

receiving a set of origin device color space data triplet values representative of each of the colors in said color image;

correcting each of said origin device color space data triplet values for printing with said printer;

forming a set of corrected origin device color space data triplet values;

creating a set of printer device color space data triplet values correlated to said origin device color space data triplet values;

creating a set of printer device halftone color space data triplet values for each of said origin device color space data triplet values adapted as output signals for printing said color image;

storing each set of said printer device halftone color space data triplet values as a separate dither matrix of cells of output signals for printing said color image such that a set of said printer device halftone color space data triplet values matrix is correlated to each said origin device color space data triplet value; and

printing said color image pixel by pixel by

receiving the origin device color space data triplet value for a pixel,

selecting the set of said printer device halftone color space data triplet values correlated to said origin device color space data triplet value,

selecting the cell of said selected set of said printer device halftone color space data triplet values correlated to said origin device color space data triplet value, and

using the output signal stored in said cell to print said color.

7. The method as set forth in claim 6, wherein said step of said printer device halftone color space data triplet values is correlated to said origin device color space data triplet values further comprises the step of:

data point values for cyan, magenta, and yellow primary colors are used for a color printing device.