Image Processing Apparatus Brightness Range Compression
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Solution Overview
Problem
Existing dynamic range compression techniques for HDR image printing can cause contrast degradation and result in excessively high output brightness values, especially when the input brightness value distribution has a large range, leading to incongruous output images.
Innovation Solution
An image processing apparatus that sets relationship information to associate input brightness values with output brightness values, ensuring that output brightness values do not exceed a predetermined value, and uses this information to generate a dynamic range compression curve that maintains contrast by assigning a wider output brightness range to areas with high appearance frequency and a narrower range to areas with low appearance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If dynamic range compression is performed using a tone curve based on brightness value distribution, then the brightness range is compressed into the printable D range, but contrast degradation occurs when the input brightness value distribution has a large range
Solution Approach 1:
The patent divides the image into multiple regions and performs dynamic range compression independently for each region. By segmenting the image processing into region-specific operations, each region can have its own optimized tone curve that preserves local contrast characteristics while achieving overall brightness range compression.
Solution Approach 2:
The patent applies different tone curves to different regions of the image based on local brightness value distributions. Instead of using a single global tone curve, each region receives a customized compression curve that adapts to its specific characteristics, thereby maintaining local contrast quality while achieving the desired brightness range compression.
2Illumination intensity
If dynamic range compression is performed using a tone curve, then the brightness range is compressed into the printable D range, but output brightness values may become extremely high depending on the input brightness value distribution
Solution Approach 1:
The patent applies clipping processing to limit output brightness values to a predetermined maximum value before final output. This preliminary restriction prevents extremely high output brightness values from occurring, ensuring stability and reliability of the output regardless of the input brightness value distribution.
Solution Approach 2:
The patent dynamically adjusts the tone curve parameters based on the input brightness value distribution characteristics. By changing the compression curve parameters adaptively, the system ensures that output brightness values remain within a stable and predictable range while still achieving effective dynamic range compression.
3Device complexity
If a single tone curve is used for the entire image, then the processing is simple, but contrast degradation occurs in regions with large brightness value ranges
Solution Approach 1:
The patent divides the image into multiple regions and generates separate tone curves for each region. This segmentation approach increases processing capability to handle local variations in brightness distribution, thereby preserving local contrast quality that would be lost with a single global tone curve.
Solution Approach 2:
The patent implements dynamic tone curve generation that adapts to the specific characteristics of each image region. Instead of using a fixed static tone curve, the system dynamically generates or selects appropriate tone curves based on local brightness value distributions, allowing the processing to adapt to varying local conditions.
Data Source
AI summary
An image processing apparatus sets, for at least one portion of a first image in which a brightness range is a first range, relationship information which associates an input brightness value with an output brightness value, changes, based on the relationship information, brightness values of pixels in the portion, and outputs a second image which has a second range of brightness. The relationship information is generated so as to associate, with each of the brightness values of the pixels in the portion, an output brightness value which does not exceed a value higher than the brightness value by a predetermined value, and to associate, with a brightness value which is not less than a feature amount among the brightness values of the pixels in the portion, a predetermined output brightness value falling within a predetermined range.