HDR Display Tone Mapping for Image-Dependent Brightness and Contrast
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Solution Overview
Problem
Traditional brightness and contrast controls on displays do not adequately account for the luminance characteristics of high dynamic range (HDR) images, leading to loss of details in either bright or dark parts of the image when adjustments are made.
Innovation Solution
Implementing dynamic average picture level (APL) boost to enhance dark images without affecting highlights and dynamic peak luminance reduction to adjust highlights without affecting darks, with optional combination for improved image-dependent control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixed brightness and contrast controls are applied to HDR images, then standard dynamic range images display correctly, but details are lost in either bright or dark parts of HDR images
Solution Approach 1:
The patent implements dynamic brightness and contrast controls that automatically adjust based on the luminance characteristics of each displayed image. The system calculates image-specific brightness and contrast values by analyzing the luminance histogram and applying adaptive transformations, allowing the display to optimize HDR image presentation without requiring manual user adjustment for each image type.
Solution Approach 2:
The system changes the brightness and contrast parameters dynamically based on image content analysis. By computing luminance statistics and applying adaptive parameter adjustments, the display transforms fixed control settings into variable parameters that optimize image presentation for different luminance ranges while preserving details in both highlights and shadows.
2Reliability
If brightness is reduced to preserve black details, then dark areas maintain detail, but white details are lost
Solution Approach 1:
The patent applies local quality adjustments by processing different luminance regions of the image separately. The system divides the luminance histogram into distinct regions (blacks, mid-tones, highlights) and applies region-specific brightness and contrast transformations. This allows black details to be preserved through localized brightness adjustment while white details are protected through separate highlight processing, preventing information loss in either extreme.
3Reliability
If contrast is increased to preserve white details, then bright areas maintain detail, but black details are lost
Solution Approach 1:
The system applies differential contrast processing to different luminance regions. By analyzing the luminance histogram and identifying distinct regions, the patent applies contrast adjustments selectively - enhancing contrast in highlight regions to preserve white details while applying different contrast transformations to shadow regions to maintain black details, thus preventing information loss in both extremes simultaneously.
4Device complexity
If fixed brightness and contrast settings are used, then device complexity remains low, but image quality deteriorates for HDR content
Solution Approach 1:
The patent implements a self-service system where the display automatically analyzes the luminance characteristics of each image and adjusts brightness and contrast settings without user intervention. The system computes luminance histograms, identifies image-specific optimal parameters, and applies adaptive transformations autonomously, eliminating the need for complex manual control interfaces while maintaining high HDR image quality.
Data Source
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AI summary
Methods and systems to adjust differently brightness and contrast for dark and bright pictures on a display are provided. Given a tone-mapping curve mapping an input dynamic range to a display comprising a minimum and maximum display luminance value, the maximum display luminance value is lowered to an adjusted luminance value according to user defined parameters. The input dynamic range is tone-mapped to the display dynamic range using the adjusted luminance value. For brightness control, the tone mapped image is stretched linearly back to the maximum display luminance value. For contrast control, a gamma or power EOTF of the display is adjusted according to the adjusted luminance. For displays with global backlight control, the global backlight is adjusted only when contrast is adjusted.