Image Processing Apparatus Dynamic Range Compression Contrast Preservation
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Solution Overview
Problem
Dynamic range compression in HDR image printing often results in lowered contrast due to the inherent characteristics of gray scale conversion, particularly when the output brightness range is narrower than the input range, making it challenging to maintain image quality.
Innovation Solution
An image processing apparatus that divides the input image into multiple areas based on the ratio of the output to input brightness ranges, adjusting the number of areas to ensure a more uneven distribution of brightness values, thereby associating high-frequency input brightness values with wider output ranges to compress the dynamic range while preserving contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gray scale conversion is used to compress dynamic range from first range to second range, then the brightness range is successfully compressed to match printing apparatus capabilities, but the contrast of the image is lowered
Solution Approach 1:
The image is divided into multiple areas based on brightness value distributions. Each area is processed independently with area-specific gray scale conversion parameters, allowing contrast preservation in each segment while achieving overall dynamic range compression across the entire image
Solution Approach 2:
Different gray scale conversion characteristics are applied to different areas of the image based on their local brightness distributions. High-contrast areas maintain their contrast through optimized conversion curves, while low-contrast areas receive appropriate compression, achieving local optimization of both contrast and dynamic range adaptation
2Ease of manufacture
If the output brightness range is made narrower to match printing apparatus D range, then the printing capability is optimized, but the contrast in the converted image deteriorates
Solution Approach 1:
The image processing divides the image into multiple areas and applies different gray scale conversion parameters to each area. This segmentation allows the output brightness range to be compressed to match printing apparatus capabilities while preserving contrast within each local area through area-specific conversion curves
Solution Approach 2:
The gray scale conversion parameters are dynamically adjusted based on the brightness value distribution in each area. By changing conversion parameters locally rather than applying a uniform conversion, the system achieves both narrow output brightness range for printing and preserved contrast through parameter optimization
Data Source
AI summary
An image processing apparatus for converting a first image having a first range of a brightness into a second image having a second range of the brightness narrower than the first range obtains information of sizes of the first range and the second range, divides the first image based on the information such that the number of areas obtained by dividing the first image when a ratio of the second range to the first range is a first value becomes smaller than that when the ratio is smaller than the first value, sets, for each of the areas, relationship information that associates input brightness values in the first range with output brightness values in the second range, and converts brightness values of pixels included in the first image into brightness values of pixels of the second image based on the relationship information.