HDR Thumbnail Generation with Gamma Preservation
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Solution Overview
Problem
High dynamic range (HDR) moving images cannot be displayed as thumbnail images at HDR quality when recorded in the same format as standard dynamic range (SDR) moving images, as only 8-bit thumbnail images can be recorded, limiting the bit depth of HDR images.
Innovation Solution
An image processing apparatus and method that acquires a moving image and generates a thumbnail image with a gamma equal to the original image and a bit depth lower than the original, specifically converting 10-bit HDR images to 8-bit for thumbnail generation and display, while maintaining gamma and color gamut accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HDR moving images are recorded in the same format as SDR moving images to maintain compatibility, then compatibility with SDR moving images is improved, but the thumbnail image quality deteriorates because only 8-bit thumbnail images can be recorded instead of 10-bit HDR images
Solution Approach 1:
The patent applies preliminary action by generating a thumbnail image from the HDR moving image before final storage, and performing bit depth conversion during this preliminary generation phase. The thumbnail is created with appropriate bit depth reduction (from 10-bit to 8-bit) while maintaining gamma characteristics, so that when the HDR moving image is stored in an SDR-compatible format, the thumbnail is already optimized for display without requiring subsequent processing that would compromise image quality.
2Adaptability or versatility
If the bit depth of HDR images is reduced for thumbnail generation, then the thumbnail can be displayed in SDR format, but image quality may deteriorate due to loss of HDR information
Solution Approach 1:
The patent applies local quality by treating the thumbnail generation process differently from the main HDR moving image storage. Instead of uniformly reducing the entire HDR sequence to 8-bit, the patent selectively processes only the thumbnail portion by performing bit depth conversion from 10-bit to 8-bit while preserving the gamma characteristics. This localized processing ensures the thumbnail is compatible with SDR displays without compromising the quality of the main HDR content.
Solution Approach 2:
The patent applies parameter changes by modifying specific parameters (bit depth and gamma) during thumbnail generation. The bit depth is changed from 10-bit to 8-bit to enable SDR compatibility, while the gamma parameter is maintained to preserve the perceptual quality and avoid banding artifacts. This selective parameter modification allows the thumbnail to be displayed in SDR format while maintaining visual quality.
3Adaptability or versatility
If gamma conversion is performed during thumbnail generation from HDR images, then the thumbnail can be displayed on SDR devices, but banding artifacts may occur and color accuracy deteriorates
Solution Approach 1:
The patent applies inversion by reversing the conventional approach of converting HDR to SDR through gamma correction. Instead of applying gamma conversion to adapt the image to SDR displays, the patent maintains the gamma characteristics of the original HDR image during thumbnail generation. This inverted approach prevents the introduction of banding artifacts and color inaccuracies that typically result from gamma conversion, while still enabling SDR display compatibility through bit depth reduction alone.
Data Source
AI summary
An image processing apparatus comprising at least one memory and at least one processor which function as: an acquisition unit configured to acquire a moving image; and a generation unit configured to generate a thumbnail image from the moving image, wherein in a case where the moving image is a high dynamic range (HDR) moving image, the generation unit generates the thumbnail image of which gamma is equal to a gamma of the moving image and bit depth is lower than a bit depth of the moving image.