SDR to HDR Image Processing via Adaptive Luminance Expansion
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Solution Overview
Problem
Existing methods for converting digital image colors from Standard Dynamic Range (SDR) to High Dynamic Range (HDR) are not adapted to images with extreme contrast and brightness levels, resulting in an artificial and unfaltering appearance.
Innovation Solution
A processing method that determines a global brightness level of an image, calculates an expansion exponent as a decreasing function of this brightness level, and transforms the luminance components of the image to adapt it to a display device with a wider dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If global non-linear intensity expansion operators are applied to convert SDR to HDR, then the dynamic range of the display device is utilized, but the image rendering becomes artificial and unrealistic for images with extreme contrast and brightness levels
Solution Approach 1:
The patent applies local adaptive tone mapping by dividing the image into local regions and applying different expansion parameters to each region based on its characteristics. This allows the conversion to adapt to local variations in brightness and contrast, preserving realistic rendering while utilizing HDR capabilities.
Solution Approach 2:
The patent introduces dynamic parameter adjustment where the expansion exponent and other conversion parameters are not fixed but adapt dynamically based on the input image characteristics. This enables the system to optimize the conversion process for different image types, avoiding artificial rendering while maximizing HDR display potential.
2Productivity
If simple linear operators are used for luminance expansion, then real-time processing is achieved, but the perceived quality improvement is limited for images with extreme contrast
Solution Approach 1:
The patent changes the parameters of the tone mapping operator dynamically based on image characteristics such as brightness level and contrast. By adjusting the expansion exponent and other parameters according to the input image properties, the system achieves both real-time processing and high perceived quality for images with extreme contrast.
Solution Approach 2:
The patent incorporates feedback mechanisms where the conversion process monitors the output image quality and adjusts parameters accordingly. This feedback loop ensures that the real-time processing maintains high perceived quality by adapting to the specific characteristics of each image being processed.
Data Source
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AI summary
The invention relates to a method for processing at least one digital image with a view to its rendition on a display device, said image comprising image elements, an image element being associated with colour information represented in a first colorimetric space comprising a luminance component and chrominance components, said luminance component having a value included in a first predetermined interval of values, said display device being able to render values of luminance components of the image elements included in a second predetermined interval of values, of greater length than that of the first interval, said method comprising the steps of: Determination (El) of an item of information representative of an overall brightness level of the image perceived by an observer, on the basis of the values of the first luminance component of the elements of the image; Calculation (E2) of an expansion exponent (y) as a function of the overall brightness level item of information determined; Transformation (E3) of the first luminance components of the elements of the image into second luminance components, comprising for an element of the image, the calculation of an intermediate luminance value by applying the calculated expansion exponent to the first luminance component value and multiplying the intermediate value calculated by the length of the second interval of predetermined luminance values. According to the invention, the calculated expansion exponent is a decreasing function of the overall brightness level item of information determined.