Edge/Boundary extraction from the image

I am trying to extrcat the outer boundary of the image attached here. Could someone help me with how to do this is in matlab.

Answer 1

[Jonas]

you can e.g. convert it to grayscale and then use the edge() function. there are many parameters you can try

after you got the binary edge image you may have a look into bwareafilt() function

[Turbulence Analysis]

Thanks for the suggestion, Jonas,

Let's say my real image is saved in the matrix B, I tried as shown below .

However, I couldn't able to get the desired edge profile using bwareafilt() . I have also attached B.mat for your reference. Please provide your views

% Real image to rgb conversion 
rgb1 = ind2rgb(B,jet(1024));
imagesc(rgb1);
% rgb to gray conversion
grayimage = rgb2gray(rgb1);
imagesc(grayimage);
Edge = edge(grayimage, 'sobel');
imagesc(Edge);

[Jonas]

i had a look into the image, maybe you try

rgb1 = ind2rgb(B,jet(1024));
redimage = rgb1(:,:,1);
imagesc(redimage);
Edge = edge(grayimage, 'sobel');
imagesc(bwconvhull(Edge));

this uses the red channel instead of gray image and forms a convex hull of the edge points

hiw exactly you may (pre)process your image depends also on where exactly is your outer bound is. is it the red part or already the yellowish part farther outside?