Display Device HDR Tone Mapping for Local Contrast
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Solution Overview
Problem
Existing display devices struggle to accurately express a wide range of brightness levels in digital images, leading to improper representation of dark and bright areas, particularly in HDR images, resulting in biased contrast balance and reduced realism.
Innovation Solution
A display device and method that utilizes histogram information for tone mapping, including histogram equalization processing and local tone mapping to adjust luminance, generating adaptive local contrast curves for each area, enhancing contrast ratio and detail.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If HDR images with 16-bit or 32-bit brightness range are used, then brightness expression range is improved, but general display devices cannot express the full range and require conversion to limited dynamic range
Solution Approach 1:
The patent divides the image processing into multiple stages: first performing global tone mapping to convert HDR to SDR, then performing local tone mapping on specific regions. This segmentation allows the system to handle the wide brightness range of HDR images while adapting to the limited capabilities of standard displays, resolving the contradiction between brightness range and device complexity.
Solution Approach 2:
The patent applies different processing strategies to different regions of the image. By identifying regions with significant brightness differences and applying local tone mapping specifically to those areas, the system optimizes contrast and detail where needed while maintaining overall brightness accuracy, thus resolving the contradiction between comprehensive brightness expression and processing complexity.
2Adaptability or versatility
If conventional tone mapping is applied to convert HDR to SDR, then compatibility with display devices is improved, but contrast ratio and detail in local areas are degraded
Solution Approach 1:
The patent segments the tone mapping process into global and local components. Global tone mapping ensures compatibility with standard SDR displays, while local tone mapping is applied to specific regions to preserve or enhance contrast and detail. This two-stage approach resolves the contradiction between display compatibility and local image quality.
Solution Approach 2:
The patent performs global tone mapping first to establish baseline compatibility with SDR displays, then applies local tone mapping as a subsequent enhancement step. This preliminary action ensures that the image is already compatible with standard displays before applying localized improvements, thus resolving the contradiction between compatibility and local quality.
3Reliability
If saturation level is maintained high during tone mapping, then color vibrancy is improved, but margin for contrast ratio and detail enhancement is reduced
Solution Approach 1:
The patent applies different processing intensities to different regions. In areas where contrast enhancement is prioritized, saturation is adjusted to provide sufficient margin for detail enhancement. In other areas, color vibrancy is maintained. This localized approach resolves the contradiction between overall color vibrancy and local contrast enhancement capacity.
Solution Approach 2:
The patent applies saturation adjustment selectively rather than uniformly across the entire image. By applying partial action only where needed for contrast enhancement while maintaining saturation elsewhere, the system preserves both color vibrancy and the capacity for local detail enhancement, resolving the contradiction between these two qualities.
Data Source
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.