《数字图像处理 Digital Image Processing》课件 Spatial Domain Enhancement[精品].ppt

The two-dimensional Laplacian is obtained by summing these two components: Discrete Laplacian expression Lecture 7: Chapter 3 Spatial Domain Enhancement Filter masks for different Laplacian Lecture 7: Chapter 3 Spatial Domain Enhancement Definition of isotropic filters: The response is independent of the direction of the discontinuities in the image to which the filter is applied. Isotropic filters are rotation invariant, in the sense that rotating the image and then applying the filter gives the same result as applying the filter to the image first and then rotating the result. Concept of Rotation Invariability Lecture 7: Chapter 3 Spatial Domain Enhancement Illustration of isotropic filters and its counterpart Sobel operator is not an isotropic derivative operator. Lecture 7: Chapter 3 Spatial Domain Enhancement The Laplacian is an isotropic derivative operator Illustration of Laplace filter Lecture 7: Chapter 3 Spatial Domain Enhancement Laplacian characteristics: uniform features are lost. Solution: Adding the Laplacian image to the original image. How to apply the Laplacian to sharpen images Note: If the Laplacian has a negative center coefficient, then we subtract the Laplace image from the original. Lecture 7: Chapter 3 Spatial Domain Enhancement We summarize below: If the center coefficient of the mask is negative If the center coefficient of the mask is positive g(x,y) = The Laplacian application summary Lecture 7: Chapter 3 Spatial Domain Enhancement A=imread(Fig3.40(a).jpg); imshow(A); h=[0 -1 0;-1 4 -1;0 -1 0] B=mov_msk(A,h); figure, imshow(B); C=imadd(A,B); figure, imshow(C); Demo h1=[0 1 0; 1 -4 1;0 1 0] B1=mov_msk(A,h1); figure, imshow(B1); C1=imadd(A,B1); figure, imshow(C1); C2=imsubtract(A,B1); figure, imshow(C2); by plug in expanded Laplacian, We get: The above equation can be implemented using the mask (composite Laplacian mask) shown in this figure. Derive composite Laplacian mask simplify Lecture 7: Chapter 3 Spatial Domain Enhancemen