Launch an algorithm in several samples extracted from an image

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Rdmato33 2015-10-13

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https://ww2.mathworks.cn/matlabcentral/answers/248369-launch-an-algorithm-in-several-samples-extracted-from-an-image

评论： Thorsten 2015-10-14

Hello, I would like to extract features of a raster image by using an active contour algorithm (see below). My goal is to obtain morphometry of each object. For each of them (92 features), I have created same size matrix (5 rows, 5 columns) with this code :

   %svf is the name of the image
   %xy_points are the center coordinates of each feature
   For m=1:92;a(:,:,m)=svf(xy_points(m,1)-2:xy_points(m,1)+2,xy_points(m,2)-2:xy_points(m,2)+2);end

Thus, I obtained 92 matrix of 5x5.

This is my problem : I have succeeded in applying the active contour algorithm on 1 image (the whole image called "svf"). But I don't know how to apply it on my samples (matrix for each feature) and to repeat the process.

Thanks for your help.

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Answer 1

Thorsten 2015-10-13

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Why not

for m=1:92;
  result = activecontour(svf(xy_points(m,1)-2:xy_points(m,1)+2,xy_points(m,2)-2:xy_points(m,2)+2));
   % do something with result
end

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Rdmato33 2015-10-13

编辑：Rdmato33 2015-10-13

在 MATLAB Online 中打开

Thanks for you answer. Actually, I use a different algorithm than "activecontour". As you can see below, the code is more complex. Do I have to insert your code at the beginning of the algorithm (at the step of resizing)?

     imwrite(svf,'../images/svf.pgm');  
     [I,map] = rawread('../images/svf.pgm');  
     I=imresize(I,1);
     disp(' Compute edge map ...');
     f = 1 - I/255; 
     f0 = gaussianBlur(f,1);
     [px,py] = gradient(f0);
     figure(1); 
     subplot(121); imdisp(-f); title('snake potential');
     subplot(122); quiver(px,py); 
     axis('image', 'ij', 'off');    
     title('traditional force');
     disp(' ');
     disp(' Press any key to start the deformation');
     pause;
     figure(1); subplot(121);  
     colormap(gray(64)); 
     image(((1-f)+1)*40); axis('square', 'off');
     figure, imshow(I,map);
     colormap(gray(64)); 
     t = 0:0.5:1;
     x = 120
     y = 20
     [x,y] = snakeinterp(x,y,2,0.5);
     snakedisp(x,y,'r') 
     pause(1);
     for i=1:20,
       [x,y] = snakedeform2(x,y,0.05,0,1, 2, 0.15,px,py,5);
       [x,y] = snakeinterp(x,y,2,0.5);
       snakedisp(x,y,'r') 
       title(['Deformation in progress,  iter = ' num2str(i*5)])
       pause(0.1);
     end
     disp(' ');
     disp(' Press any key to display the final result');
     pause;
     figure(1); subplot(121);  
     colormap(gray(64)); 
     image(((1-f)+1)*40); axis('square', 'off');
     snakedisp(x,y,'r'); 
     title(['Final result,  iter = ' num2str(i*5)]);

Thorsten 2015-10-14

Your code has various issues:

. if you have swf as your image, why do you write it to a pgm image, then read it, instead on just working with swf

. why to you scale with 1, i.e., no scaling?

Besides this, my suggestion was to write a function activecontour with the image as an argument, that you then call in a loop over all your subimages.

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