Methods and apparatus for converting color values

• US 6,950,110 B2
• Filed: 07/23/2004
• Issued: 09/27/2005
• Est. Priority Date: 05/24/2002
• Status: Expired due to Term

• Current Assignee: Fiery LLC
• Original Assignee: Electronics For Imaging Incorporated
• Inventors: Falk, Richard
• Primary Examiner(s): Bella, Matthew C.
• Assistant Examiner(s): RAHMJOO, MANUCHEHR
• Application Number:
  US10/897,958
• Publication Number:
  US 20040257379A1
• Time in Patent Office: 431 Days
• Field of Search: 345/589, 345/601, 345/600, 345/606
• US Class Current: 345/589
• 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 color conversion system for converting a first color value to a second color value, the system comprising:

a first module comprising an input coupled to the first color value, a lookup table coupled to the input and to an interpolator, the lookup table comprising a plurality of entries, each entry associating a first value to a second value, the interpolator coupled to an output; and

a second module comprising a decompressor comprising an input coupled to the output of the first module, and an output providing the second color value;

wherein the lookup table is created by;

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

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

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

2. The system of claim 1, wherein the first color value comprises a plurality of color values and the second color value comprises a plurality of color values.

3. The system of claim 1, wherein the first color value comprises Red (R), Green (G) and Blue (B) color values.

4. The system of claim 1, wherein the second color value comprises Cyan (C), Magenta (M) and Yellow (Y) color values.

5. The system of claim 1, wherein the decompressor comprises a plurality of one-dimensional lookup tables.

6. The system of claim 5, wherein the second color value comprises a plurality of color values, and each one-dimensional lookup table is coupled to a corresponding one of the plurality of color values.

7. The system of claim 1, wherein the second values are compressed using a linear compression formula.