White Balance Gain Estimation Using Specular Reflection Components
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Solution Overview
Problem
Conventional image processing methods for digital cameras face challenges in accurately estimating illuminant colors, leading to reduced accuracy in white balance adjustment, especially in images without white objects or those with small luminance differences.
Innovation Solution
An image processing apparatus and method that extracts pixels within a predetermined color space, separates specular reflection components, and calculates white balance gains based on both extracted pixels and specular reflection components to improve the accuracy of illuminant color estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional white balance methods extract white pixels from the image, then the process is simple, but the accuracy of illuminant color estimation deteriorates when the image does not include white objects or includes many objects close to but not white
Solution Approach 1:
The patent segments the pixel extraction process into two distinct parts: extracting pixels within a predetermined color range (white balance candidates) and extracting specular reflection components separately. By dividing the white balance calculation into multiple independent extraction processes, the system can handle images without white objects more effectively while maintaining overall process simplicity.
Solution Approach 2:
The patent combines multiple types of pixel data (white balance candidate pixels from color space extraction and specular reflection pixels from highlight detection) to form a composite dataset for illuminant color estimation. This composite approach ensures accurate white balance calculation even when traditional white objects are absent, as the system can rely on specular reflection components alone or in combination with available color pixels.
2Illumination intensity
If the image has small luminance difference (dynamic range), then the dynamic range is limited, but the accuracy of white balance adjustment deteriorates
Solution Approach 1:
The patent changes the parameters used for white balance calculation by incorporating specular reflection component extraction in addition to traditional color space extraction. This parameter expansion allows the system to utilize highlight information even when overall luminance differences in the image are small, thereby maintaining accurate illuminant color estimation in low-contrast scenarios.
3Device complexity
If only white pixel extraction is used for white balance calculation, then the process is simple, but the reliability of white balance adjustment deteriorates in challenging image conditions
Solution Approach 1:
The patent segments the white balance processing into distinct functional modules: a first extraction unit for white balance candidate pixels, a second extraction unit for specular reflection components, and a calculation unit that integrates both. This segmentation maintains operational simplicity while significantly improving reliability in challenging conditions through multi-source data integration.
Solution Approach 2:
The patent introduces specular reflection component extraction as an intermediary process that bridges the gap between limited color information and accurate illuminant estimation. This intermediary extraction provides additional reliable data points (highlight pixels) that mediate the calculation of white balance gains, especially when traditional white pixel extraction is insufficient.
Data Source
AI summary
An image processing apparatus is provided that allows accurate white balance gains to be obtained by accurately estimating the illuminant colors of various objects in an image. The white balance gains are obtained based on values of white pixels that have been extracted from an input image and have colors included in an extraction range, and the white balance gains are obtained based on specular reflection components included in the input image, are mixed in accordance with a mix ratio. The mix ratio is determined in accordance with, for example, a degree of reliability of extraction of the white pixels.