Image Contrast Enhancement via Luminance-Dependent Gain Curves
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Solution Overview
Problem
Existing image processing technologies face issues with reducing contrast in bright and dark part gradations while maintaining apparent contrast, and often result in changes in hue and color saturation during gradation conversion processing.
Innovation Solution
An image processing program that performs gradation conversion processing with a gain curve that adjusts contrast enhancement based on luminance information, using a non-transitory computer-readable storage medium to enhance local contrast by generating blurred images and applying specific gain curves for pixel processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gradation conversion processing using an S-shaped curve is performed, then contrast is enhanced, but the contrast of the bright part gradation is reduced or the dark part gradation is shadowed and blocked up
Solution Approach 1:
The patent applies different processing characteristics to different luminance regions of the image. By dividing the gradation conversion into multiple segments with different curve characteristics, it enhances contrast in intermediate tones while preserving highlight and shadow details, thus resolving the contradiction between overall contrast enhancement and local gradation quality
Solution Approach 2:
The gradation conversion curve is segmented into multiple regions (highlight, intermediate, shadow) with different conversion characteristics. This segmentation allows independent optimization of each region, preventing the uniform S-curve from degrading highlight and shadow areas while enhancing intermediate contrast
2Productivity
If gradation conversion processing using an S-shaped curve is performed on each of the R, G, B values, then contrast is enhanced, but the hue and color saturation of each of the bright part gradation, the intermediate part gradation, and the dark part gradation change
Solution Approach 1:
The patent applies different gradation conversion characteristics to different luminance regions (highlight, intermediate, shadow) while maintaining consistent color relationships. By controlling the conversion differently for each luminance zone, it preserves color accuracy in critical regions while still achieving contrast enhancement where appropriate
Solution Approach 2:
The patent uses dynamic gradation conversion where the conversion characteristics change based on the input luminance level. This dynamic approach allows the system to maintain color accuracy in regions where it matters most while still providing contrast enhancement in intermediate tones
3Productivity
If contour enhancement processing is performed with a large radius, then contours are enhanced, but the change in color saturation becomes conspicuous or the blown out highlights of the bright part gradation become more likely to occur
Solution Approach 1:
The patent applies contour enhancement with different radius parameters to different regions of the image. By using smaller radii in highlight areas and larger radii in intermediate tone areas, it achieves effective contour enhancement while preventing color saturation changes and highlight blowing out in sensitive regions
Data Source
AI summary
A non-transitory computer-readable storage medium storing an image processing program causing a computer to execute an image processing on image data to be processed, the image processing program including an obtaining step obtaining the image data, a gradation conversion processing step performing gradation conversion processing on the image data at an intermediate part of gradation according to input/output characteristics having characteristics to which characteristics to reduce a contrast are added, and a correcting step making a correction to enhance a local contrast indicative of contrast at a local part of an image for the image data subjected to the gradation conversion processing by using a gain curve in which a degree of enhancement changes in accordance with luminance information of a pixel to be processed, and thus, bright and dark part gradations are improved while suppressing a change in a hue and color saturation as well as maintaining an apparent contrast.