Auto Brightness Control Using RGB Histogram Analysis
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Solution Overview
Problem
Existing image photographing devices face challenges in controlling image brightness effectively, leading to saturation and dark photographing effects, especially when using CMOS image sensors in bright environments, as they rely solely on Y data for brightness control, which limits the adjustment of color balance and results in suboptimal image quality.
Innovation Solution
A method and apparatus that calculate a histogram for the image, determine the brightness average, and adjust exposure and gain to maintain the brightness within a preset range by using a combination of R, G, and B data, preventing saturation and ensuring adequate grayscale distribution, thereby improving image quality and auto-white balance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only Y data is used for brightness control, then the brightness control process is simple, but image saturation and dark photographing effects occur
Solution Approach 1:
The patent changes the parameter basis for brightness control from using only Y data to using a combination of R, G, and B data. This allows the system to calculate brightness average, standard deviation, and histogram distribution using multiple color channels, preventing saturation and dark photographing effects while maintaining reliable image quality across different lighting conditions
2Device complexity
If Y data only is used for brightness adjustment, then the control method is simple, but color balance adjustment is limited
Solution Approach 1:
The patent makes the brightness control system multi-functional by using R, G, and B data simultaneously. The same data combination serves both brightness control and color balance adjustment purposes, allowing the Auto White Balance function to improve performance while the brightness control handles multiple aspects including brightness average, standard deviation, and histogram distribution
3Illumination intensity
If brightness control is performed in bright environments with large light quantity, then exposure is adequate, but image saturation occurs
Solution Approach 1:
The patent implements feedback control by calculating the standard deviation of brightness values and the histogram distribution of R, G, and B data. When the standard deviation exceeds a threshold or histogram distribution indicates potential saturation, the system adjusts exposure time and gain parameters to prevent saturation while maintaining adequate exposure in bright environments
Data Source
AI summary
A method for automatically controlling image brightness in an image photographing device by calculating a histogram for an image; obtaining a brightness average for the histogram; determining if a number of pixels of a histogram distribution within a first range and a number of pixels of a histogram distribution within a second range are included within a preset range; and when the number of pixels of the histogram distribution within the first range and the number of pixels of the histogram distribution within the second range are included within the preset range, as a result of a determination, adjusting the brightness average to be a reference brightness.