Gamut Compression Lookup Table for Color Gradation Preservation
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Solution Overview
Problem
Existing gamut compression techniques either compress all colors, leading to loss of gradation, or only compress colors outside the destination gamut, resulting in insufficient gradation expression.
Innovation Solution
A gamut compression method that uses a lookup table to map color data from a first gamut to a second gamut, enhancing the difference in color components or attributes to maintain gradation, ensuring that multiple output values become distinct in the second gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If clipping technique is used to compress only colors outside the destination gamut, then faithful reproduction of reproducible colors is improved, but gradation expression becomes insufficient
Solution Approach 1:
The patent changes the parameter being compressed from color values alone to a combination of color values and position information. By encoding position data (indicating whether a color is within or outside the gamut) alongside compressed color values, the system maintains both faithful color reproduction and gradation expression. The lookup table stores tuples of (compressed_color, position) where position distinguishes between in-gamut and out-of-gamut colors, allowing the decoder to preserve subtle variations in out-of-gamut regions while accurately reproducing in-gamut colors.
2Loss of information
If compression technique is used to compress all colors, then relative color relationship and gradation expression are maintained, but faithful reproduction of colors within destination gamut deteriorates
Solution Approach 1:
The patent applies different compression strategies to different regions of the color space. For colors within the destination gamut, no compression is applied (identity mapping), ensuring faithful reproduction. For colors outside the gamut, compression is applied but with position information preserved to maintain gradation. The lookup table implements this by storing (original_color, compressed_color, position) tuples where in-gamut colors have compressed_color equal to original_color and out-of-gamut colors have transformed values with position flags indicating their status.
Data Source
AI summary
A gamut compressing device for compressing video data in a first gamut into video data in a second gamut. The device includes a compression unit compressing a value of color data in the first gamut, not contained in the second gamut, into a value of color data contained in the second gamut through a predetermined compression calculation. A gradation generating unit generates gradation such that a plurality of values of color data having the same value as a result of the compression become different in the second gamut.