Hairline contour locating method for precise face ROI extraction
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Solution Overview
Problem
Existing methods for detecting the hairline contour of a face image are imprecise, especially when the hairline is irregular, leading to incomplete region of interest (ROI) and potential miss detection of skin regions.
Innovation Solution
A method involving the use of a color model to detect the skin region, followed by elimination of narrow protrusions and hair interference, and calculation of grayscale differences to adjust the initial hairline contour, ensuring precise outlining of the hairline using a 'three courts and five eyes' proportion for accurate ROI extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ellipse fitting is used to obtain the face region of interest, then the detection process is simple, but the hairline contour cannot be precisely outlined especially when left and right fringes are irregular
Solution Approach 1:
The patent segments the face detection process into multiple stages: initial ellipse fitting to obtain rough face region, followed by hairline contour detection within that region, and finally ROI extraction using the precise hairline contour. This segmentation allows each stage to focus on its specific task, achieving both simplicity and precision.
Solution Approach 2:
The patent performs preliminary ellipse fitting to obtain an initial face region before conducting the more complex hairline contour detection. This preliminary action establishes a search boundary that simplifies subsequent processing while enabling precise hairline outlining through the two-stage approach.
2Area of stationary object
If the fitted ellipse is made larger to include all forehead skin region, then complete skin region coverage is achieved, but hair interference is brought to the region of interest
Solution Approach 1:
The patent extracts the hairline contour as a separate boundary from the overall face ellipse. By detecting the hairline contour within the initial face region and using it to define the precise ROI, the method excludes hair areas from the final skin region of interest while maintaining complete forehead skin coverage.
Solution Approach 2:
The patent transitions from a static ellipse-based ROI definition to a dynamic two-stage process where the ROI is first approximated by an ellipse and then precisely adjusted by detected hairline contour. This dynamic adjustment allows the ROI boundary to adapt to actual hairline positions, excluding hair interference while covering all skin regions.
3Object-affected harmful factors
If the fitted ellipse is made smaller to exclude hair, then hair interference is reduced, but it is impossible to obtain all the forehead skin region as the region of interest
Solution Approach 1:
The patent extracts the hairline contour as a distinct boundary feature and uses it to precisely define the ROI. This extraction allows the system to identify and exclude only the hair regions while including all forehead skin regions, solving the contradiction between reducing hair interference and maintaining complete skin coverage.
4Productivity
If traditional color model and ellipse fitting method is used, then the processing speed is fast, but the region of interest is incomplete leading to miss detection of skin regions
Solution Approach 1:
The patent segments the detection process into two phases: a fast initial phase using color model and ellipse fitting to obtain rough face region and hairline contour, followed by a precise ROI extraction phase. This segmentation maintains high processing speed in the first phase while ensuring detection completeness in the second phase through accurate hairline-based ROI definition.
Data Source
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AI summary
This application provides a method and an apparatus for positioning a hairline contour, and a computer-readable storage medium. The method includes: obtaining a to-be-detected face image; generating an initial hairline contour of the to-be-detected face image; calculating, in a grayscale image, a difference between grayscale values of a pixel on the initial hairline contour and a surrounding neighboring pixel; and adjusting the initial hairline contour based on the difference between the grayscale values, to generate an accurate hairline contour of the to-be-detected face image. According to technical solutions provided in this application, the hairline contour of the face image can be precisely outlined, so that all forehead skin can be obtained as an ROI the face.