Active Contour algorithm applicated to Digital Elevation Model

Hello, I am using Chenyang Xu and Jerry Prince active contour algorithm in order to obtain the geometry of bomb craters from a digital elevation model. I have extracted central points of each crater (circular structures - see image) and I want to draw the contour line of those craters from the central points.

I try to use this code (see below) but I want to draw the contour line from coordinates of my central points (Not from clicked coordinates. I already have extracted the coordinates of the central points). How can I do that?

Thanks

   % My image is called "svf.pgm"
   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); [x,y] = getpts;
     colormap(gray(64)); 
     t = 0:0.5:1;
     [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)]);

[Abdalla Artaime]

Hi dear, How you got the local minimum points Thanks

[Abdalla Artaime]

please let me know Can you help me

Answer 1

[Image Analyst]

Can't you just use contour() on your topographic image? You can mask out the non-crater background region if you want so that you see contours only within the craters.

[Rdmato33]

Actually, I just need morphometry data of every crater like perimeter, major and minor axis, excentricity, and so on. The way to obtain it is to draw an active contour.

[Image Analyst]

Oh, okay. So when you use activecontour() and get your binary image, then just use regionprops() to get those measurements. See my Image Segmentation Tutorial: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862 for how to get those measurements.

See my activecontour demo, attached, if you or anyone needs a demo of that.

[Rdmato33]

Great explanation. Thank you for your help.

Answer 2

[Abdalla Artaime]

Hi dear, How you got the local minimum points Thanks

Answer 3

[Abdalla Artaime]

please let me know. Can you help me