Color Balance Correction Using Third Highlight Color
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Solution Overview
Problem
Conventional color balance correction methods for digital images often result in incorrect light source estimation, leading to unstable and extreme adverse effects, particularly when the color of bright regions deviates from the expected values, causing improper color balance corrections.
Innovation Solution
An image processing apparatus and method that calculates a third highlight color based on the positional relationship between the first and second highlight colors in a color space, allowing for stable color balance correction even when one of the initial highlight colors is incorrect, by using a third highlight color for conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light source estimation is performed using gray and skin color pixels, then color balance correction can be applied, but the light source estimation may be wrong when the image does not include skin color regions
Solution Approach 1:
The patent introduces highlight color as an intermediary element to bridge light source estimation and color balance correction. Instead of directly estimating light source from gray and skin color pixels alone, the method uses highlight color (brightest region color) as a mediator that reflects light source characteristics, thereby improving estimation accuracy while maintaining versatility across different image types including those without skin color regions
2Adaptability or versatility
If color balance correction is performed using highlight color of bright regions, then the correction can be applied to various images, but it may incorrectly judge images with proper color balance when the highlight color is chromatic
Solution Approach 1:
The patent implements a feedback mechanism where the estimated light source color temperature is used to generate a reference white point, which then serves as a basis for evaluating whether the highlight color judgment is appropriate. This feedback loop allows the system to distinguish between chromatic highlight colors that indicate color fog versus those that represent proper color balance under specific lighting conditions, thereby improving judgment accuracy while maintaining versatility
3Productivity
If conventional color balance correction methods are used, then processing can be performed, but extreme adverse effects occur when the color of bright regions deviates from expected values
Solution Approach 1:
The patent performs preliminary determination of the reference white point based on estimated light source color temperature before executing the color balance correction. This preliminary action establishes a reliable reference framework in advance, allowing the subsequent correction process to proceed stably even when highlight colors deviate from expected values, thereby preventing extreme adverse effects while maintaining processing efficiency
Data Source
AI summary
An image processing apparatus for applying a color balance correction to input image data, comprises a first highlight color calculation unit which estimates a light source at the time of shooting from pixel values of the image data, converts color values of the image data based on a condition of the estimated light source at the time of shooting, and calculates a first highlight color; a second highlight color calculation unit which calculates a second highlight color from the image data; a third highlight color calculation unit which calculates a third highlight color based on a positional relationship between the first highlight color and the second highlight color on a color space; and a correction unit which attains the color balance correction by converting the pixel values of the image data using the third highlight color.