gvf.rar_GVF_GVF matlab_Gradient Vector Flow_active contour_flow

% EXAMPLE GVF snake examples on two simulated object boundaries. % % NOTE: % % traditional snake and distance snake differed from GVF snake only % by using different external force field. In order to produce the % corresponding external force field, use the following (all % assuming edge map f is in memory). % % traditional snake: % f0 = gaussianBlur(f,1); % [px,py] = gradient(f0); % % distance snake: % D = dt(f>0.5); % distance transform (dt) require binary edge map % [px,py] = gradient(-D); % % [px,py] is the external force field in both cases % % balloon model using a different matlab function "snakedeform2" % instead of "snakedeform". The external force could be any force % field generated above. % % an example of using it is as follows % [x,y] = snakedeform2(x,y, alpha, beta, gamma, kappa, kappap, px,py,2); % do a "help snakedeform2" for more details % Chenyang Xu and Jerry Prince 6/17/97 % Copyright (c) 1996-97 by Chenyang Xu and Jerry Prince cd ..; s = cd; s = [s, '/snake']; path(s, path); cd examples; help gvf_ex; % ==== Example 1: U-shape object ==== % Read in the 64x64 U-shape image [I,map] = rawread('../images/U64.pgm'); % Compute its edge map disp(' Compute edge map ...'); f = 1 - I/255; % Compute the GVF of the edge map f disp(' Compute GVF ...'); [u,v] = GVF(f, 0.2, 80); disp(' Nomalizing the GVF external force ...'); mag = sqrt(u.*u+v.*v); px = u./(mag+1e-10); py = v./(mag+1e-10); % display the results figure(1); subplot(221); imdisp(I); title('test image'); subplot(222); imdisp(f); title('edge map'); % display the gradient of the edge map [fx,fy] = gradient(f); subplot(223); quiver(fx,fy); axis off; axis equal; axis 'ij'; % fix the axis title('edge map gradient'); % display the GVF subplot(224); quiver(px,py); axis off; axis equal; axis 'ij'; % fix the axis title('normalized GVF field'); % snake deformation disp(' Press any key to start GVF snake deformation'); pause; subplot(221); image(((1-f)+1)*40); axis('square', 'off'); colormap(gray(64)); t = 0:0.05:6.28; x = 32 + 30*cos(t); y = 32 + 30*sin(t); [x,y] = snakeinterp(x,y,3,1); % this is for student version % for professional version, use % [x,y] = snakeinterp(x,y,2,0.5); snakedisp(x,y,'r') pause(1); for i=1:25, [x,y] = snakedeform(x,y,0.05,0,1,0.6,px,py,5); [x,y] = snakeinterp(x,y,3,1); % this is for student version % for professional version, use % [x,y] = snakeinterp(x,y,2,0.5); snakedisp(x,y,'r') title(['Deformation in progress, iter = ' num2str(i*5)]) pause(0.5); end disp(' Press any key to display the final result'); pause; cla; colormap(gray(64)); image(((1-f)+1)*40); axis('square', 'off'); snakedisp(x,y,'r') title(['Final result, iter = ' num2str(i*5)]); disp(' '); disp(' Press any key to run the next example'); pause; % ==== Example 2: Room like object ==== % Read in the 64x64 room image [I,map] = rawread('../images/room.pgm'); % Compute its edge map disp(' Compute edge map ...'); f = 1 - I/255; % Compute the GVF of the edge map f disp(' Compute GVF ...'); [px,py] = GVF(f, 0.2, 80); % display the results figure(1); subplot(221); imdisp(I); title('test image'); subplot(222); imdisp(f); title('edge map'); % display the gradient of the edge map [fx,fy] = gradient(f); subplot(223); quiver(fx,fy); axis off; axis equal; axis 'ij'; % fix the axis title('edge map gradient'); % display the GVF subplot(224); quiver(px,py); axis off; axis equal; axis 'ij'; % fix the axis title('GVF field'); % snake deformation disp(' Press any key to start GVF snake deformation'); pause; figure(1); subplot(221); colormap(gray(64)); image(((1-f)+1)*40); axis('square', 'off'); t = 0:0.5:6.28; x = 32 + 3*cos(t); y = 32 + 3*sin(t); [x,y] = snakeinterp(x,y,2,0.5); snakedisp(x,y,'r'); pause(1); for i=1:15, [x,y] = snakedeform(x,y,0.05,0,1,2,px,py,5); [x,y] = snakeinterp(x,y,2,0.5); snakedisp(x,y,'r') title(['Deformation in progress, iter = ' num2str(i*5)]) pause(0.5); end disp(' Press any key to display the final result'); pause; figure(1); subplot(221); colormap(gray(64)); image(((1-f)+1)*40); axis('square', 'off'); snakedisp(x,y,'r'); title(['Final result, iter = ' num2str(i*5)]);