Se-Hoon Park 26 th August 2014 Backgrounds for feature extraction Table of contents Edge detection -> Canny edge detector A combined corner and edge detector.A combined corner and edge detector. C Harris, M Stephens - Alvey vision conference, 1988 (citation : 9984)C Harris Corner detection -> Harris corner detector A computational approach to edge detection J CannyJ Canny - Pattern Analysis and Machine Intelligence, IEEE, 1986 (citation:19512) Edge detection -> Canny edge detector Corner detection -> Harris corner detector Canny edge Sobel filtering I : intensity of image Canny edge Canny edge Sobel filtering Canny edge Direction of gradient x y Non maximum suppression Suppression Suppression Magnitude of gradient Direction of gradient Canny edge Double thresholding noiseWeak edgeStrong edge Double threshold Double threshold Edge tracking by hysteresis Edge detection -> Canny edge detector Corner detection -> Harris corner detector Canny edge Harris corner What is corner? flat no change in all directionedge no change along the edge directioncorner significant change in all directions Canny edge Harris corner Canny edge Harris corner Harris corner detection Canny edge Harris corner properties Rotation invariance Partial intensity invariance Canny edge Harris corner Problem Non-invariant image scale Lowe, D.G., "Distinctive image features from scale-invariant keypoints", IJCV Canny edge Harris corner Scale space Scale invariance scale , scale invariant . SIFT Laplacian , scale invariant .