电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 3.Edge l Models Edge of Image (Objects) Ideal step edge Ideal ramp edge Roof edge abc FIGURE 10.8 From left to right, models (ideal representations)of a step,a ramp,and a roof edge,and their corresponding intensity profiles
Ideal step edge Ideal ramp edge Roof edge 3. Edge Models ◼ Edge of Image (Objects)
电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 3.Edge l Models FIGURE 10.9 A 1508 X 1970 image showing (zoomed)actual ramp (bottom,left),step (top,right),and roof edge profiles.The profiles are from dark to light,in the areas indicated by the short line segments shown in the small circles.The ramp and"step" profiles span 9 pixels and 2 pixels,respectively.The base of the roof edge is 3 pixels. (Original image courtesy of Dr.David R.Pickens,Vanderbilt University.)
3. Edge Models
电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 3.Edge I Models ab FIGURE 10.10 (a)Two regions of constant intensity Horizontal intensity separated by an profile ideal vertical ramp edge. (b)Detail near the edge,showing a horizontal First intensity profile, derivative together with its first and second derivatives. Second derivative (1)it produces two values for every edge in an image(an undesirable feature); Zero crossing (2)its zero crossings can be used for locating the centers of thick edges
3. Edge Models (1) it produces two values for every edge in an image (an undesirable feature); (2) its zero crossings can be used for locating the centers of thick edges
电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 3.Edge Models intensity 1st derivative 2nd derivative Three fundamental 6=0.0 steps performed in edge detection 6=0.1 M抽 1) Image smoothing for noise reduction. 6=1.0 Detection of edge points. 6=10.0 Edge localization. d山 FIGURE 10.11 First column:Images and intensity profiles of a ramp edge corrupted by random Gaussian noise of zero mean and standard deviations of 0.0,0.1,1.0,and 10.0 intensity levels,respectively.Second column:First-derivative images and intensity profiles.Third column:Second-derivative images and intensity profiles
3. Edge Models ① Image smoothing for noise reduction. ② Detection of edge points. ③ Edge localization. ❖ Three fundamental steps performed in edge detection intensity 1 st derivative 2 nd derivative = 0.0 = 0.1 =1.0 =10.0
电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 4.Basic edge detection The image gradient and its properties Gradient operators Combining the gradient with thresholding
The image gradient and its properties Gradient operators Combining the gradient with thresholding 4. Basic edge detection