METHODS AND APPARATUS FOR CONVERTING COLOR VALUES

• US 20070285435A1
• Filed: 08/20/2007
• Published: 12/13/2007
• Est. Priority Date: 05/24/2002
• Status: Active Grant

• Current Assignee: Fiery LLC
• Original Assignee: Electronics For Imaging Incorporated
• Inventors: Falk, Richard
• Granted Patent: US 7,756,346 B2
• Time in Patent Office: Days
• US Class Current: 345/600
• CPC Class Codes: G06F 3/13 Digital output to plotter ; Cooperation and interconnection of the plotter with other functional units
• CPC Class Codes: G09G 2340/02 Handling of images in compressed format, e.g. JPEG, MPEG
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables
• CPC Class Codes: H04N 1/6019 using look-up tables H04N1/6025 takes precedence

Abstract

Color conversion apparatus and methods are provided for converting a first color value, such as an RGB, L*a*b* or XYZ color value, to a second color value, such as an RGB, CMY, CMKY, L*a*b*, L,C₁C₂, or XYZ color value, without saturation error.

Claims

1. A computer readable carrier comprising computer program instructions structured to cause a computer to convert a first color value to a second color value, wherein the instructions cause the machine to:

provide a lookup table comprising a plurality of entries, each entry associating a corresponding first value to a corresponding second value;

identify an entry that has a corresponding second value equal to a predetermined value, and that is adjacent an entry having a corresponding second value equal to a number other than the predetermined value;

compress the corresponding second values of a first plurality of the entries to form corresponding intermediate values; and

replace the corresponding second value of the identified entry with a value determined by a regression that includes the corresponding intermediate value of the adjacent entry.

2. The computer readable carrier of claim 1, wherein the instructions are further structured to cause the computer to:

identify each entry that has a corresponding second value equal to a predetermined value, and that is adjacent an entry having a corresponding second value equal to a number other than the predetermined value; and

replace the corresponding second value of each of the identified entries with a value determined by a regression that includes the corresponding intermediate value of the corresponding adjacent entry.

3. The computer readable carrier of claim 1, wherein each of the corresponding second values has a value greater than or equal to zero (“

ZERO”

) and less than or equal to a maximum number (“

MAX”

).

4. The computer readable carrier of claim 3, wherein the predetermined value is ZERO.

5. The computer readable carrier of claim 3, wherein the predetermined value is MAX.

6. The computer readable carrier of claim 1, wherein each of the corresponding second values has a value greater than or equal to zero (“

ZERO”

) and less than or equal to a maximum number (“

MAX”

), and wherein the instructions are further structured to cause the computer to;

identify a first entry that has a corresponding second value equal to ZERO, and that is adjacent a second entry having a corresponding second value equal to a number greater than ZERO, and identifying a third entry that has a corresponding second value equal to MAX, and that is adjacent a fourth entry having a corresponding second value equal to a number less than MAX; and

replace the corresponding second value of the first entry with a value determined by a regression that includes the corresponding intermediate value of the second entry, and replacing the corresponding second value of the third entry with a value determined by a regression that includes the corresponding intermediate value of the fourth entry.

7. The computer readable carrier of claim 1, wherein the instructions are further structured to cause the computer to:

identify a fifth entry that has a corresponding first value equal to the first color value; and

set an intermediate color value equal to the corresponding intermediate value of the fifth entry.

8. The computer readable carrier of claim 7, wherein the instructions are further structured to cause the computer to decompress the intermediate color value to provide the second color value.

9. The computer readable carrier of claim 1, wherein the instructions are further structured to cause the computer to:

identify a second plurality of entries that have corresponding first values that surround the first color value; and

set an intermediate color value equal to a value determined by interpolating the corresponding intermediate values of the second plurality of entries.

10. The computer readable carrier of claim 9, wherein the instructions are further structured to cause the computer to decompress the intermediate color value to provide the second color value.