Reduced 3D LUT Nonlinear Interpolation for HDR Color Gamut Mapping

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Solution Overview

Problem

Display devices with limited dynamic range and color gamut struggle to accurately render High Dynamic Range (HDR) or wide color gamut content, leading to interpolation errors and suboptimal picture quality when trying to display HDR images or videos.

Innovation Solution

The method employs a reduced 3-D look-up table (LUT) for non-linear interpolation to convert HDR or wide color gamut pixels to Standard Dynamic Range (SDR) pixels, using polynomial coefficients and tetrahedral or tri-linear interpolation to minimize errors and preserve image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a full-size LUT is used to map HDR color gamut to SDR color gamut, then color accuracy is improved, but memory requirements and device complexity increase significantly

Engineering Contradiction:

Improvecolor accuracyVSAvoidmemory requirements

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The color gamut mapping is divided into multiple sub-cubes, each representing a portion of the overall color space. Instead of using a single large LUT, the method segments the HDR color gamut into smaller regions and applies separate interpolation to each sub-cube, reducing the memory burden while maintaining color accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different interpolation methods (tetrahedral or tri-linear) are applied to different sub-cubes based on their local color characteristics. This allows the system to optimize for color accuracy in regions where it matters most while using simpler interpolation in other regions, balancing quality and resource usage.

Inventive Principle:

Principle #3Local quality

2Productivity

If linear mapping is used to simplify color gamut conversion, then processing speed is improved, but color accuracy deteriorates due to interpolation errors

Engineering Contradiction:

Improveprocessing speedVSAvoidcolor accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The method employs non-linear interpolation techniques (tetrahedral or tri-linear) that account for the curved nature of color gamut boundaries, replacing simple linear mapping. This curvature-based approach better preserves color relationships while maintaining acceptable processing speeds through efficient algorithms.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The LUT is pre-computed and stored in memory, allowing the runtime processing to simply perform lookups and interpolation rather than calculating complex color transformations on the fly. This preliminary preparation separates the computationally intensive work from the real-time processing requirement.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11115563B2Method and apparatus for nonlinear interpolation color conversion using look up tables

Publication Date: 2021.09.07 ATI TECHNOLOGIES ULC

AI summary

A method and apparatus obtains a source image having a plurality of source color gamut pixels in a source color gamut. The method and apparatus converts the plurality of source color gamut pixels to a plurality of corresponding target color gamut pixels using non-linear interpolation of a plurality of output pixel values from a reduced 3-D look-up table (LUT) for a target color gamut. The method and apparatus provides, for display, the plurality of target color gamut pixels (e.g., one or more pixels) on a target color gamut display.