Dynamic Range Mapping Function for Image Hue Preservation
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Solution Overview
Problem
Existing image conversion methods using inverse Tone Mapping (iTM) suffer from hue and saturation changes, as well as color contour issues due to linear mapping functions, which require multiple points to form curves, leading to step differences in dynamic range conversion.
Innovation Solution
An electronic device employing a curve-type mapping function based on display and scene luminance characteristics, using a piecewise linear function with smoothing filters to convert dynamic ranges while maintaining hue and saturation, by applying gain values to primary colors and adjusting intermediate tone levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a linear mapping function is used to convert LDR/SDR image to HDR image, then the conversion process is simple, but the converted image exhibits hue and saturation changes and color contour due to step difference
Solution Approach 1:
The patent applies a curve-type mapping function instead of a linear mapping function to convert LDR/SDR images to HDR images. The curve-type function uses multiple control points to define a smooth transition, eliminating the step differences and color contours that occur with linear functions while maintaining computational feasibility.
Solution Approach 2:
The patent changes the parameters of the mapping function from linear to curve-type by introducing multiple control points (first control point, second control point, third control point, fourth control point) that define the curve shape. This parameter change allows smooth interpolation between luminance values, preserving hue and saturation while achieving accurate color conversion.
2Manufacturing precision
If a curve-shaped mapping function is used to improve color accuracy, then hue and saturation are preserved, but multiple points are required to form the curve increasing complexity
Solution Approach 1:
The patent applies different mapping characteristics to different regions of the luminance range by using multiple control points positioned at specific locations (including black level, white level, and intermediate points). Each control point locally defines the curve behavior for its corresponding luminance region, allowing precise color preservation without requiring the entire curve to be complex.
Solution Approach 2:
The mapping function is segmented into multiple linear segments between control points, with each segment handling a specific portion of the luminance range. This segmentation allows the curve to be constructed from simpler linear pieces while maintaining overall smoothness and color accuracy, reducing the computational burden compared to a single complex curve.
3Manufacturing precision
If multiple control points are used to form a curve mapping function, then color contours are reduced, but step differences remain due to discrete point connections
Solution Approach 1:
The patent uses a curve-type mapping function with multiple control points that are strategically positioned to define a smooth continuous curve. The curve passes through or near the control points while maintaining smooth transitions, eliminating the discrete step-like connections that would occur with simple point-to-point linear interpolation. This curved approach ensures uniform color distribution and smooth luminance transitions.
Data Source
AI summary
An electronic device and an image conversion method of the electronic device, the electronic device comprising: a receiving unit for receiving a first image from a source device; a decoding unit for decoding brightness information of the first image; a converting unit for converting a dynamic range of the first image on the basis of the decoded brightness information, using a mapping function; and a display unit for displaying a second image having the converted dynamic range on a display, wherein the mapping function is a curve function including a plurality of points determined on the basis of the first image, a characteristic of a change in brightness of a display of the source device, and a characteristic of brightness of a scene of the first image. The present disclosure may generate, for example, a high dynamic range (HDR) image, which is improved from a standard dynamic range (SDR) image.