Image Exposure Control Using Face and Dark Region Brightness
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Solution Overview
Problem
Conventional automatic exposure methods in image processing fail to maintain image quality, particularly when capturing human faces in environments with insufficient light or strong backlight, leading to overexposure or underexposure issues.
Innovation Solution
An image processing method and device that includes an image capturing unit, an image processing unit, an image recognition unit, and an exposure adjusting unit, which generates average brightness values for both the dark parts and human faces in an image, using a weight array to calculate an exposure value and adjust the exposure accordingly to ensure proper illumination and detail preservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional automatic exposure process is used, then the exposure value is calculated based on the whole picture or center weighted method, but the particular area of the image such as human face becomes too dark or too bright resulting in poor image quality
Solution Approach 1:
The patent divides the image into multiple regions of interest (ROIs) including human face area, dark part area, and other areas. By segmenting the image this way, the exposure calculation can focus on specific regions rather than using overall average or center-weighted methods, allowing precise exposure control for critical areas like human faces even when they occupy small portions of the image.
Solution Approach 2:
The patent applies different exposure strategies to different regions of the image. When a human face is detected in a specific ROI, the system calculates exposure value based on the brightness of that local region (human face area) rather than the entire image. This local quality approach ensures that critical areas receive appropriate exposure adjustment while maintaining overall image quality.
2Reliability
If the human face is not found by the camera in environments with strong backlight, then the image cannot be obtained, but conventional exposure methods cannot adjust exposure based on face brightness
Solution Approach 1:
The patent performs face detection and ROI identification as preliminary actions before exposure calculation. By first identifying where the human face is located in the image and creating corresponding ROIs, the system prepares the necessary information for subsequent exposure adjustment. This preliminary action ensures that when exposure calculation occurs, the system already has the spatial information needed to apply appropriate exposure values to the correct regions.
Solution Approach 2:
The system uses the detected face location and brightness information as feedback to adjust the exposure value. When a human face is detected in a specific ROI, the brightness of that region feeds back into the exposure calculation, allowing the system to dynamically adjust exposure parameters based on the actual lighting conditions of the face area rather than relying on predetermined or overall image brightness.
3Device complexity
If exposure value is calculated via whole picture or center weighted method, then the calculation is simple, but the particular area such as human face cannot present original appearance due to overexposure or underexposure
Solution Approach 1:
The patent segments the image into multiple ROIs including human face area, dark part area, and other areas. This segmentation increases the complexity of the calculation process but enables precise exposure control for critical areas. The system calculates exposure value based on the brightness of specific regions (particularly human face area) rather than using simple overall average or center-weighted methods, thereby improving image quality while maintaining manageable computational complexity through structured region-based processing.
Data Source
AI summary
An image processing method applied in an image processing device, which includes an image capturing unit, an image processing unit, an image recognition unit and an exposure adjusting unit, is provided. The image processing method includes the following steps: obtaining a first image by the image capturing unit, generating an average brightness of a dark part of the first image by the image processing unit; recognizing the first image by the image recognition unit; generating a first average brightness of a human face by the image processing unit and generating a first exposure value according to the average brightness of the dark part of the first image, the first average brightness of the human face and a weight array, when the human face is recognized from the first image; and adjusting an exposure of the first image according to the first exposure value by the exposure adjusting unit.