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Stanford University
EE368 Face detection
Joon Hyung Shim, Jinkyu Yang, and Inseong Kim
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Introduction
Face detection : important part of face recognition
Variations of image appearance pose (front, non-front) occlusion Image orientation illuminating condition facial expression.
Methods color segmentation image segmentation template matching methods.
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Color Segmentation RGB components YCbCr components
Y = 0.299R + 0.587G + 0.114B
Cb = -0.169R - 0.332G + 0.500B
Cr = 0.500R - 0.419G - 0.081B
Skin window : from mean, deviation of Cb, Cr components.
Skin pixel of YCbCr color space
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Color segmentation result of a training image
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Image Segmentation
Separate the image blobs into individual regions
Fill up black isolated holes, remove white isolated region Separate some integrated regions into individual faces
Roberts cross edge detection algorithm Highlights regions(edge) black line erode
Previous images are integrated into one binary image
Small black and white areas are removed.
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Roberts cross edge detection
gradient magnitude : |G | = ( Gx2 + Gy
2 ) ½ or |G | = |Gx | + |Gy |
Angle of orientation : θ = arctan (Gy /Gx ) - 3π/4
Pseudo-convolution operator
magnitude : |G | = |P1 – P4 | + |P2 – P3 |
Pseudo-Convolution masks
Roberts Cross convolution masks
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Preliminary face detection with red marks
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Image Matching
Eigenimage Generation 10 eigenimages using 106 test
Average image using eigenimages
Building Eigenimage Database 30 220 pixel-width square image with 10-pixel gap
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Image Matching (cont.)
Test Image Selection : box-merge algorithm
Merging of Adjacent Boxes
Correlation : image matching algorithm Normalized test image : gray , average brightness of skin color
Distance compensation
->
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Image Matching (cont.)
Filtering using Statistical Information : non-face removal
Histogram : Imaging matching
Correlation Ranking after Geographical Consideration
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Results
Face Detection Results using 7 Training Images
Right hit rate : 93.3 %
Repeat rate : 0 %
False hit rate : 4.2 %
The average run time : 96 seconds.
numFaces numHit numRepeat
numFalse run time[sec]
Training_1.jpg 21 19 0 0 111
Training_2.jpg 24 24 0 1 101
Training_3.jpg 25 23 0 1 89
Training_4.jpg 24 21 0 1 84
Training_5.jpg 24 22 0 0 93
Training_6.jpg 24 22 0 3 100
Training_7.jpg 22 22 0 1 95
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Conclusion Color segmentation
Rectangular window must be in actual distribution of skin color
Image segmentation Unnecessary noises in edge integration Roberts cross operator : small-hole removal Sobel cross filter, prewitt filter Threshold : discriminate face edges from other edge lines
effectively
Skin-colored areas : unnecessary squares one face Eigenimage matching Statistical approach
Sophisticated algorithm for general applications
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Gender RecognitionFace Detection
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