Alpha Channel Bilateral Filtering for Image Artifact Reduction

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Solution Overview

Problem

Compression techniques for image content often introduce artifacts and reconstruction errors, particularly in the alpha channel, which are not effectively mitigated by existing deblocking filters.

Innovation Solution

A method and apparatus for alpha channel post processing using a bilateral filter, tailored to the level of compression, to improve image quality by filtering alpha channel values and generating a reconstructed image.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If compression techniques are applied to image content, then data size is reduced and rendering speed is improved, but artifacts and reconstruction errors are introduced in the alpha channel

Engineering Contradiction:

Improverendering speedVSAvoidimage quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent separates the alpha channel processing from color channel processing, applying dedicated bilateral filtering specifically to the alpha channel. This segmentation allows targeted artifact reduction in the alpha channel without affecting color channels, resolving the contradiction between compression speed and alpha channel quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies bilateral filtering with specific parameters (spatial sigma and range sigma) tailored to the alpha channel characteristics. By adjusting these filtering parameters, the system reduces compression artifacts while maintaining rendering efficiency, thus improving image quality without sacrificing productivity.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If deblocking filters are applied to compressed images, then some artifacts are reduced, but alpha channel artifacts such as ringing or mosquito noise are not effectively mitigated

Engineering Contradiction:

Improveartifact reductionVSAvoidfilter effectiveness

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies different filtering strategies to different channels: standard deblocking filters for color channels and specialized bilateral filtering for the alpha channel. This local quality approach ensures each channel receives appropriate artifact reduction, making the overall system more adaptable to channel-specific characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The bilateral filter acts as an intermediary processing step specifically for the alpha channel after decompression. This intermediary filtering operation targets alpha channel artifacts without interfering with color channel processing, effectively mitigating ringing and mosquito noise that standard deblocking filters cannot address.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If aggressive compression is applied to the alpha channel, then data size is further reduced, but visible artifacts and loss of detail increase

Engineering Contradiction:

Improvedata sizeVSAvoiddetail preservation

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent converts the harmful effect of aggressive compression (which introduces artifacts) into a benefit by applying bilateral filtering that specifically targets and removes these artifacts. The filtering process transforms the compressed, artifact-ridden alpha channel into a cleaner output, allowing aggressive compression to be used without sacrificing perceived quality.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent replaces traditional mechanical deblocking filter mechanisms with a bilateral filtering approach that uses spatial and range sigma parameters to selectively smooth alpha channel values. This substitution enables more effective artifact reduction while preserving detail, allowing greater compression aggression without quality loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12167046B2Alpha channel post processing in image coding

Publication Date: 2024.12.10 GOOGLE LLC

AI summary

Alpha channel post processing in image coding can include decoding, from multiple color channels of a bitstream, color channel values for an encoded image, decoding, from an alpha channel of the bitstream, alpha channel values for the encoded image, determining a bilateral filter based on a level of compression for encoding the alpha channel, post processing the alpha channel values by filtering the alpha channel values using the bilateral filter to obtain filtered alpha channel values, and generating at least a portion of a reconstructed image corresponding to the encoded image using the filtered alpha channel values and the color channel values.