Color Conversion Apparatus for Rec 2020 to Rec 709 Mapping
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Solution Overview
Problem
There is a need to convert digital images or video signals from one colour space to another, such as from Rec 2020 to Rec 709, without causing undesirable changes in hue, brightness, and saturation, as certain colours in the source space are not representable in the target space.
Innovation Solution
A colour conversion apparatus and method that uses matrix multiplication for direct mapping, followed by processing to detect and adjust colour components, applying gain and offset values, and inhibiting components from exceeding maximum representable values, ensuring accurate conversion while maintaining colour integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If direct mapping using matrix multiplication is used to convert from Rec 2020 to Rec 709 colour space, then conversion speed and simplicity are improved, but colour accuracy deteriorates because certain colours in the source space are not representable in the target space
Solution Approach 1:
The patent applies preliminary action by detecting out-of-gamut colours before final conversion and applying selective processing to preserve colours that cannot be directly represented in the target colour space, thereby preventing colour accuracy deterioration before it occurs
Solution Approach 2:
The patent applies local quality by treating different colour components differently - only adjusting the green colour component while leaving red and blue components unchanged, thereby maintaining colour accuracy for representable colours while handling non-representable colours appropriately
2Adaptability or versatility
If colour components are adjusted to fit within target colour space ranges, then representability in target space is improved, but hue, brightness and saturation changes increase
Solution Approach 1:
The patent applies local quality by selectively adjusting only the green colour component (G) while leaving red (R) and blue (B) components unchanged. This localized adjustment ensures that colours are adapted to fit within the target colour space ranges without causing unnecessary changes to hue, brightness and saturation
Solution Approach 2:
The patent applies parameter changes by modifying specific colour component values (particularly the green component) within defined ranges to ensure representability in the target colour space while minimizing deviations from original colour characteristics
Data Source
AI summary
Color conversion apparatus comprises mapping circuitry configured to map pixels of an input image having color components in an input color space to pixels of an mapped image having color components in an output color space, the input color space and the output color space being different color spaces such that at least a subset of colors representable in the input color space are not representable in the output color space; processing circuitry configured to process the mapped image by detecting instances, in the color components of pixels of the mapped image, of representations of negative amounts of a color component and in response to such a detection in respect of a pixel under test, to increase all of the color components of the pixel under test by an amount of at least the magnitude of the greatest magnitude negative amount of the color components of that pixel under test; and output circuitry configured to generate pixels of an output image, having color components in the output color space, from pixels of the processed mapped image, the output circuitry being configured to inhibit color components of pixels of the output image from exceeding a maximum representable color amount.