Image Contrast Enhancement via Layered Segmentation and Local Gain
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Solution Overview
Problem
Current image contrast enhancement methods, such as global tone reproduction, global histogram equalization, homomorphic filtering, and multi-scale Retinex algorithms, suffer from issues like loss of image contrast in certain regions, unnatural output, unclear image edges, and halo phenomena.
Innovation Solution
An apparatus and method that divide an input image into at least two layers with different detail degrees and perform contrast enhancement on each layer at varying degrees, using edge-preserving filtering and distinct luminance gain functions to enhance image contrast effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If global tone reproduction method is used for image contrast enhancement, then the overall image contrast is improved, but the contrast of part of image regions is lost making the image look faded
Solution Approach 1:
The patent divides the input image into multiple layers including a background layer and detail layers with different filtering coefficients. This segmentation allows different contrast enhancement strategies to be applied to different layers, preserving both overall contrast improvement and local contrast information.
Solution Approach 2:
The patent applies different luminance gain functions to different layers: a first luminance gain function for the background layer and a second luminance gain function for the detail layers. This local differentiation ensures that contrast enhancement is optimized for each layer's specific characteristics, preventing loss of local contrast information.
2Illumination intensity
If global histogram equalization method is used for image contrast enhancement, then the image contrast is enhanced, but the output image becomes unnatural
Solution Approach 1:
By segmenting the image into background and detail layers, the patent avoids applying uniform histogram equalization to the entire image. Instead, contrast enhancement is applied selectively to different layers, preserving the natural appearance while improving contrast.
Solution Approach 2:
The patent uses luminance gain functions with adjustable parameters to control the degree of contrast enhancement applied to different layers. This allows fine-tuning of the enhancement process to maintain natural image appearance while achieving desired contrast improvement.
3Illumination intensity
If homomorphic filtering method is used for image contrast enhancement, then the image contrast is improved, but the edges of the image become unclear and a halo phenomenon is produced
Solution Approach 1:
The patent separates the image into background and detail layers using different filtering coefficients. The detail layers preserve edge information while the background layer receives contrast enhancement, preventing edge blurring and halo effects.
Solution Approach 2:
Different luminance gain functions are applied to different layers, with the detail layers receiving processing that preserves edge sharpness. This local differentiation maintains edge clarity while achieving contrast enhancement in the background regions.
Data Source
AI summary
An apparatus for image contrast enhancement and a method, electronic equipment that includes: a dividing unit configured to divide an input image into at least two layers; and detail degrees of the at least two layers are different; an enhancing unit configured to perform contrast enhancement on each of the at least two layers respectively; and degrees of enhancing contrasts of the layers are different; and a combining unit configured to combine the contrast-enhanced at least two layers. By dividing the input image into at least two layers with different detail degrees and performing contrast enhancement on the at least two layers at different degrees, the contrast of the image may be accurately and effectively enhanced, thereby a display effect of the image may be improved.