Image Processing Apparatus for HDR Video Contrast and Color Balance
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Solution Overview
Problem
Current image processing techniques for HDR displays face challenges in maintaining color balance and contrast enhancement, especially when dealing with moving images and content with localized histograms, as they often result in color imbalances and inadequate contrast improvement.
Innovation Solution
An image processing apparatus that converts input RGB signals to YCbCr signals, applies histogram equalization to the luminance signal and saturation enhancement to the color difference signals, and adjusts the histogram equalization correction intensity based on the content of each frame to maintain color balance and enhance contrast effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If histogram equalization is applied to RGB signals to enhance contrast, then the dynamic range of luminosity is widened, but color imbalances are created because the histograms of the R, G, and B color channels are widened to different extents
Solution Approach 1:
The patent segments the image processing into separate luminance and color difference components by converting RGB signals to YCbCr signals. Histogram equalization is then applied only to the luminance component (Y), while the color difference components (CbCr) are processed separately through saturation enhancement, preventing color imbalances that would occur if histogram equalization were applied directly to RGB channels.
Solution Approach 2:
The patent introduces YCbCr color space conversion as an intermediary step between RGB input and final image output. This intermediary representation separates luminance information from color information, allowing independent processing of each component and enabling histogram equalization to enhance contrast without disrupting color balance.
2Illumination intensity
If histogram equalization is applied to enhance contrast in images with localized histograms (e.g., text or charts), then the processing may not be suitable, but the need for contrast enhancement remains
Solution Approach 1:
The patent implements dynamic adaptation by analyzing the histogram characteristics of each input image and automatically adjusting the processing strategy. When the histogram is determined to be localized (as in text or charts), the system reduces or disables histogram equalization to avoid degradation, whereas for continuous histograms (natural images), full histogram equalization is applied. This dynamic adjustment enables the system to adapt to different image content types.
3Adaptability or versatility
If existing image processing techniques are applied to moving images, then the processing may not be suitable because existing techniques are typically adapted for still images
Solution Approach 1:
The patent implements periodic action by processing each frame of the moving image independently through the YCbCr conversion, histogram analysis, and selective histogram equalization pipeline. The system analyzes the histogram of each frame and applies appropriate processing on a frame-by-frame basis, enabling still-image-optimized algorithms to be effectively applied to video sequences while maintaining image quality.
Data Source
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AI summary
An image processing apparatus (10) includes an input image color space conversion unit (2) that converts an input image signal of each frame of a moving image signal into a luminance image signal and a color difference image signal, a luminance image correction unit (3) that generates a luminance-corrected image signal by applying a histogram equalization process to the luminance image signal of each frame, a color difference image correction unit (4) that generates a color-difference-corrected image signal by applying a saturation enhancement process to the color difference image signal of each frame, and an output image color space conversion unit (5) that converts the luminance-corrected image signal and the color-difference-corrected image signal into an output image signal in the same format as the input image signal. Processing by the luminance image correction unit (3) and processing by the color difference image correction unit (4) are executed in parallel with respect to each frame. The luminance image correction unit (3) adjusts a histogram equalization correction intensity of the histogram equalization process with respect to each frame.