Gamut Boundary Sampling via Inversion
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Solution Overview
Problem
Existing gamut mapping techniques require excessive computation and resources, especially when dealing with color devices with more than 3 channels, due to the need for sampling a large number of color values to accurately determine gamut boundaries.
Innovation Solution
Determining a gamut boundary description by selecting sample values in a device-independent color space and applying transforms to include only in-gamut values, forming polygonal surfaces to represent the gamut boundary, which reduces the number of samples needed as the number of colorant channels increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sample values are selected in device-dependent color space and converted to device-independent color space using a source transform, then the gamut boundary description can be determined, but the number of samples increases exponentially as the number of colorant channels increases
Solution Approach 1:
The patent inverts the conventional approach by selecting sample values in device-independent color space first, then converting them to device-dependent color space using a destination transform to check if they are in-gamut. This reverses the traditional workflow of selecting in device-dependent space and converting to device-independent space, thereby avoiding the exponential sample increase problem while maintaining gamut boundary accuracy.
Solution Approach 2:
The patent changes the parameter space from device-dependent color space to device-independent color space for sample selection. By performing sampling in the device-independent color space (which has fixed, small dimensionality) and then transforming to device-dependent space for gamut checking, the system maintains measurement precision while dramatically reducing the quantity of samples needed.
2Measurement precision
If a fine step size is used to control the accuracy of the resulting gamut boundary, then measurement precision is improved, but computational time and resources increase substantially
Solution Approach 1:
The patent changes the dimensional space in which sampling occurs from device-dependent color space (which has dimensions equal to the number of colorant channels, e.g., 3 for RGB or 6 for broader gamut devices) to device-independent color space (which has fixed 3 dimensions: L*, a*, b*). This dimensionality reduction allows for accurate gamut boundary determination with far fewer samples and less computational effort.
3Measurement precision
If sample values are selected from minimum to maximum in each colorant channel at a set interval, then the gamut boundary can be determined, but the number of samples increases to over 24 million for 6-channel devices
Solution Approach 1:
The patent changes the parameter space from device-dependent color space to device-independent color space. By sampling in the fixed 3-dimensional device-independent color space rather than in the variable high-dimensional device-dependent color space, the system achieves comprehensive gamut boundary coverage with a manageable number of samples, dramatically improving computation efficiency for multi-channel devices.
Data Source
AI summary
The present invention provides for determining a gamut boundary description for a color device, the color device being characterized at least by a destination transform which converts colors from a device-independent color space to a device-dependent color space and which reports out-of-gamut colors. A set of sample values is determined in the device-independent color space. For each of the sample values within the set of sample values, the destination transform is applied to the sample value, and in a case where the sample value is in gamut, the sample value is included within a set of gamut boundary values. The gamut boundary description is determined by forming a set of polygonal surfaces based on the set of gamut boundary values. Accordingly, a gamut boundary description is determined without necessarily having to sample additional color values as the number of colorant channels for the color device increases.