Color quantization based on desired upper bound for relative quantization step
AssigneeKWE International, Inc.
InventorSergey N. Bezryadin
Life of this patent
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Abstract
A computer system (810) receives a desired upper bound δSmax for a relative quantization step ∥S′−S″∥/∥S′∥ to be used when quantizing any color in some range of colors. Here S′ and S″ are adjacent colors in the set of colors to be made available for the quantized image, and ∥•∥ is a norm in a 70%-orthonormal linear color coordinate system, the norm being the square root of the sum of squares of the tristimulus values. The computer system determines (510) suitable quantization steps for the brightness coordinate (B) and the chromatic coordinates (e,ƒ) in a non-linear color coordinate system, and quantizes (520) the brightness and chromatic coordinates accordingly.
Claims6
A computer-readable manufacture comprising computer-readable encoding of digital data representing an image at a plurality of image portions, wherein the image comprises a plurality of image portions, wherein an image at each said image portion has color coordinates S1, S2, S3 in a first color coordinate system (CCS), wherein
- S1=√{square root over (T12+T22+T32)}
- S2=T2/S1
- S3=T3/S1
- T1, T2, T3 are color coordinates in a predefined 70%-orthonormal linear CCS;
- wherein at least for each said image portion whose color coordinate S1 is in a predefined range, the computer-readable encoding comprises color coordinates s1, s2, s3 such that:
- s1=kg·(ln(αS1)+β) rounded to an integer, where α and β are predefined constants,
- s2=keƒ·S2/S1 rounded to an integer,
- s3=keƒ·S3/S1 rounded to an integer,
- wherein keƒ is about 3·k3, or keƒ is equal to the smallest power of 2 which is greater than or equal to about 3·kB.
Dependencies are inferred from the claim text.