Luma Chroma Image Signal Processing for Dynamic Range
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Solution Overview
Problem
Digital image processing systems face challenges in capturing the full dynamic range of scenes due to lighting variations and color distortions, as they fail to accurately separate reflectance and illumination components, leading to poor image quality compared to human perception.
Innovation Solution
A modified Retinex-like method that separates the luma and chroma components of an image signal, performs multi-scale Retinex-like processing only on the luma component, and adds the processed luma component back to the chroma component to enhance dynamic range while avoiding tint shifts, using surround function values to mimic human vision capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-scale Retinex processing is applied to the entire image signal, then dynamic range accommodation is improved, but computational complexity and processor resource requirements increase
Solution Approach 1:
The image signal is segmented into luma and chroma components. The Retinex processing is applied only to the luma component, which contains the brightness information critical for dynamic range accommodation. This segmentation allows the system to achieve dynamic range improvement while avoiding the computational burden of processing the entire image signal, including the chroma component.
2Reliability
If Retinex processing is applied to the entire image signal, then dynamic range is improved, but processor resource requirements and power consumption increase
Solution Approach 1:
The image signal is divided into luma and chroma components, and Retinex processing is selectively applied only to the luma component. Since the luma component contains the essential brightness information for dynamic range perception, this selective processing achieves the desired dynamic range accommodation while significantly reducing the computational load and associated power consumption compared to processing the full image signal.
3Reliability
If prior art multi-scale Retinex processing is applied, then dynamic range is improved, but tint shifts occur in the processed image
Solution Approach 1:
The image signal is separated into luma and chroma components. By applying Retinex processing only to the luma component and leaving the chroma component unprocessed, the method preserves the original color information while still achieving dynamic range accommodation. This avoids the tint shifts that occur in prior art methods where the entire image signal is processed.
Data Source
AI summary
A method and apparatus of image processing is disclosed. The method and apparatus accomplish image processing by separating a luma component and a chroma component of an image signal. Averaging of at least some of the image pixels of the luma component is done over a plurality of image pixels to provide a plurality of surround function values. Retinex-like processing of the luma component is done using the surround function values to provide a Retinex-like processed luma component. The Retinex-like processed luma component is added to the chroma component of the image signal to provide a processed image signal.