Image Processing Apparatus HDR Contrast Correction
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Solution Overview
Problem
When printing HDR content, the difference in color reproduction ranges between the input and output devices leads to reduced contrast due to dynamic range compression and gamut mapping, resulting in lower contrast intensity.
Innovation Solution
An image processing apparatus and method that performs contrast correction by generating and applying a correction intensity based on the high-frequency components of the input and output images, using techniques like D range compression and gamut mapping, to maintain or restore the original contrast of HDR images during printing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If D range compression is performed to convert HDR luminance to standard luminance range, then the luminance range is compatible with printing apparatus, but contrast is reduced
Solution Approach 1:
The patent performs contrast correction before gamut mapping by calculating a correction luminance image that compensates for expected contrast loss. This preliminary action restores contrast in the compressed luminance image before color gamut conversion, ensuring the printed output maintains original contrast characteristics despite the necessary luminance compression
Solution Approach 2:
The patent dynamically adjusts the contrast correction intensity based on the degree of luminance compression and chromaticity characteristics. By changing the correction parameter according to the specific image content and compression ratio, the system optimizes contrast restoration while maintaining luminance range compatibility for printing
2Adaptability or versatility
If gamut mapping is performed to convert input color gamut to printing apparatus color gamut, then color reproduction is adapted to output device, but contrast intensity lowers due to compression
Solution Approach 1:
The patent performs contrast correction before gamut mapping by calculating a correction luminance image that compensates for expected contrast loss. This preliminary action restores contrast in the compressed luminance image before color gamut conversion, ensuring the printed output maintains original contrast characteristics despite the necessary luminance compression
Solution Approach 2:
The patent applies different contrast correction intensities to different chromaticity regions based on the specific gamut compression characteristics of each color region. By analyzing the chromaticity coordinates and applying localized correction, the system preserves contrast in regions that suffer greater compression while avoiding over-correction in regions with minimal compression
Data Source
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Figure 2C~2D
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AI summary
An image processing apparatus (300) comprises: obtaining means (405) for obtaining a luminance of an input image having a color reproduction range wider than that of a printing apparatus (310); conversion means (402, 403) for performing, for the input image, conversion processing of obtaining a value included in the color reproduction range of the printing apparatus and obtaining the luminance of the image after the conversion; and correction means (407) for correcting the luminance of the input image, wherein the correction means performs correction of the luminance of the input image such that an intensity of the correction becomes higher for a color that is not included in the color reproduction range of the printing apparatus than for a color included in the color reproduction range of the printing apparatus.