Display Device Tone Mapping for HDR-to-SDR Local Contrast
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Solution Overview
Problem
Standard Dynamic Range (SDR) images struggle to accurately represent both dark and bright areas due to their limited brightness range, leading to imbalanced contrast and a discrepancy between perceived scenes and captured images, while High Dynamic Range (HDR) images require conversion to SDR images, which often lose detail and contrast.
Innovation Solution
A display device and method that utilizes histogram information for tone mapping, allowing local tone mapping and histogram equalization to adjust luminance, generating adaptive local contrast curves for improved contrast ratio and detail in local areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If tone mapping is performed to convert HDR images to SDR images, then the dynamic range is reduced to match display capabilities, but the contrast ratio and detail in local areas are lost
Solution Approach 1:
The patent divides the image into multiple local areas and performs tone mapping separately for each region based on local histogram characteristics. This segmentation allows different parts of the image to retain their local contrast and detail while adapting to SDR display capabilities, resolving the contradiction between display compatibility and image quality preservation
Solution Approach 2:
The patent applies different tone mapping parameters and mapping curves to different local areas of the image based on their specific histogram distributions. This local quality approach ensures that each region is optimized for its own characteristics, preserving local contrast and detail while maintaining overall adaptability to SDR displays
2Manufacturing precision
If histogram equalization is applied to improve local contrast, then the saturation level increases causing loss of detail, but without histogram equalization the local contrast remains insufficient
Solution Approach 1:
The patent dynamically adjusts the saturation level parameter during histogram equalization based on local histogram characteristics. By changing this parameter adaptively, the system achieves improved local contrast while preventing excessive saturation that would cause detail loss, thus resolving the contradiction between local contrast enhancement and detail preservation
3Adaptability or versatility
If standard tone mapping is used to fit HDR to SDR display range, then the overall brightness range is compressed, but local contrast and three-dimensionality are degraded
Solution Approach 1:
The patent segments the image into local areas and generates separate mapping curves for each region based on local histogram analysis. This allows the overall brightness range to be adapted to SDR while preserving local contrast ratios, as each segment is independently optimized to maintain its contrast characteristics within the compressed brightness range
Solution Approach 2:
The patent introduces a local area dimension to the tone mapping process, moving from global to local processing. By adding this spatial dimension to the tone mapping operation, the system can adapt brightness range globally while preserving local contrast, thus resolving the contradiction between brightness adaptation and contrast preservation
Data Source
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AI summary
A display device and an operating method thereof are disclosed. A display device according to at least one of various embodiments of the present disclosure comprises a controller configured to perform tone mapping to adjust luminance of input image data; and a display configured to display an image according to output image data whose luminance is adjusted by the tone mapping, wherein the controller can control to lower a saturation level of the input image data on which the tone mapping is performed and perform local tone mapping.