Face Region Gain Control for Natural Image Appearance
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Solution Overview
Problem
Existing image processing techniques fail to effectively control texture, sharpness, luminance, and color of face images, particularly in low illuminance conditions and when contrast correction is performed, leading to unnatural appearances and potential underexposure.
Innovation Solution
An image processing apparatus with a face detecting section, processing controller, and specific data processing components that detect face image regions and adjust processing parameters such as gain and contrast correction based on face image information, ensuring appropriate texture, sharpness, and color correction without damaging the overall image sharpness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the gain of the addition-subtraction amplifier is increased to emphasize texture components, then the texture enhancement is improved, but the face image region becomes unnatural and induces a feeling of strangeness
Solution Approach 1:
The patent applies local quality by making the gain control spatially variable based on detected face image regions. The gain control unit sets different gain values for different regions: lower gain for face image regions to preserve natural appearance, and higher gain for non-face regions to enhance texture. This is achieved through the region specifying unit that identifies face regions and the gain control unit that adjusts amplification accordingly, resolving the contradiction between overall texture enhancement and local natural appearance.
2Reliability
If skin color region detection is used to suppress emphasis level in face regions, then the natural appearance of face images is improved, but the method fails when face images are beyond predetermined skin color range in low illuminance conditions
Solution Approach 1:
The patent changes the detection parameter from skin color chromaticity to luminance intensity. The region specifying unit detects face image regions based on luminance values rather than color information, making the system adaptable to low illuminance conditions where color detection fails. This parameter change allows the system to reliably identify face regions regardless of lighting conditions, thereby maintaining natural appearance while improving versatility.
3Manufacturing precision
If contrast correction is performed for the overall screen based on luminance information, then the overall image quality is improved, but underexposure occurs in face images
Solution Approach 1:
The patent segments the image processing into two distinct paths: overall screen processing and face-specific processing. The contrast correction unit performs luminance-based contrast correction for the entire image, while the gain control unit simultaneously applies region-specific gain adjustment to face regions detected by the region specifying unit. This segmentation allows global image quality improvement while protecting face regions from underexposure through differential gain control.
4Manufacturing precision
If color saturation, color tone, or contrast correction is performed for the overall screen, then the overall image appearance is improved, but the face image correction induces a feeling of strangeness
Solution Approach 1:
The patent applies local quality by implementing region-specific gain control that overrides or modulates global color and contrast corrections in face regions. The gain control unit uses luminance-based face region detection to identify areas where natural appearance must be preserved, then applies differential gain adjustment to prevent the strangeness effect while allowing overall image enhancement in non-face regions.
Data Source
AI summary
An image processing apparatus includes: a data processing section which processes input image data and obtains output image data; a face detecting section which detects a face image on the basis of the input image data and obtains information about a face image region in which the face image exists; and a processing controller which controls the process of the data processing section on the basis of the information about the face image region obtained in the face detecting section.