how to extract the borders of an image (OCT/retinal scan image)

Question

I have an (OCT) image like shown below (original). As you can see, it mainly has 2 layers. I want to produce an image (shown in the 3rd picture), in which the red line indic

Answer 1

The following set of instructions (using Matlab Image processing toolbox) seems to work well for your image:

1. Blur your image (Im) with a median filter to decrease the noise:

   ImB=medfilt2(Im,[20 20]);
   

2. Find the edges using sobel mask and dilate them a little bit to connect close components, and 'clean' the overall image to get rid of small areas

   edges = edge(ImB,'sobel');    
   se = strel('disk',1);
   EnhancedEdges = imdilate(edges, se);    
   EdgeClean = bwareaopen(EnhancedEdges,1e3);
   

   

3. You then have your two zones, that you can detect separately using bwlabel

   L=bwlabel(EdgeClean);
   

4. Finally, plot the two zones corresponding to L=1 and L=2

   [x1 y1] = find(L==1);
   [x2 y2] = find(L==2);
   plot(y1,x1,'g',y2,x2,'r')
   

   

There are not a lot of steps because your initial image is quite nice except from the noise. You may need to play a bit on the parameters as I started from a downloaded version of your image which can be of lesser quality than the original one. Of course this is a minimal code, but I still hope this will help.