Tone Mapping Spatial Frequency Segmentation

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Solution Overview

Problem

Existing tone mapping techniques for high-dynamic range (HDR) images on limited-dynamic range (LDR) displays often result in dynamic range compression, halo artifacts, and time-consuming manual adjustments, especially in motion pictures where variations between sequential images exacerbate these issues.

Innovation Solution

Tone mapping each object in an image or animation frame separately based on its surface, separating illumination values into low and high spatial frequency components and adjusting them independently to eliminate halo effects and preserve gradients, allowing for seamless tone mapping across a sequence of frames without introducing low frequency artifacts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If global tone mapping operators are used to convert HDR images to LDR displays, then the entire image can be mapped using consistent parameters, but this results in dynamic range compression causing saturated or too dark areas that look flat and dull

Engineering Contradiction:

Improveautomated tone mappingVSAvoidimage quality

Core Design Contradiction:

Extent of automationVSManufacturing precision

Solution Approach 1:

The patent segments the tone mapping process by separating illumination values into low spatial frequency components (handled by global operator) and high spatial frequency components (handled by local operator), allowing each to be processed with appropriate parameters to avoid the drawbacks of using either operator alone

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If local tone mapping operators are used to preserve local gradients, then illumination value gain changes can be applied locally, but this generates halo or ringing effects around brightly-colored objects against dark backgrounds

Engineering Contradiction:

Improvelocal gradient preservationVSAvoidhalo artifacts

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent segments the illumination values into spatial frequency components, applying local operators only to high spatial frequency components while using global operators for low spatial frequency components, thereby preserving local gradients without generating halo artifacts

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different tone mapping operators to different spatial frequency components: global operators for low frequency components and local operators for high frequency components, optimizing the approach for each component's characteristics

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If manual adjustments are made to correct visual artifacts after global or local tone mapping, then image quality can be improved, but this becomes an arduous and time-consuming task

Engineering Contradiction:

Improveimage qualityVSAvoidprocessing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent segments the tone mapping process to automatically combine the strengths of global and local operators, producing an output that requires minimal or no manual adjustment, thereby reducing time-consuming manual intervention while maintaining high image quality

Inventive Principle:

Principle #1Segmentation

4Productivity

If variations between sequential images are processed using conventional tone mapping, then each frame can be tone mapped independently, but this exacerbates halo effects and introduces low frequency artifacts in animation sequences

Engineering Contradiction:

Improveframe processing efficiencyVSAvoidlow frequency artifacts

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the tone mapping process into frequency-based components and applies different operators to each component, which eliminates halo effects and low frequency artifacts in animation sequences while maintaining efficient frame-by-frame processing capability

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8237730B1Tone mapping for motion pictures

Publication Date: 2012.08.07 PIXAR CORP

AI summary

A method for rendering an image including objects defined by surfaces. A rendering application selects an object in a first image and determines a surface of the object. An initial set of illumination values is calculated and is separated into low and high spatial frequency components associated with the surface of the object. The rendering application independently adjusts the illumination values of the low and high spatial frequency components based lighting information in the first image, and generates a modified set of illumination values by combining the adjusted low and high spatial frequency components. The surface of the object is then rendered using the modified set of illumination values. Advantageously, embodiments of the invention provide techniques for rendering an object without introducing halo effects around the object. Additionally, embodiments of the invention provide for rendering a sequence of frames without introducing fluctuations in the low frequency components from across frame.