How do I extract outer and inner contour in an image? Is there a inbuilt function available or do I have to do it from scratch?

I am trying to extract inner contour of an Image. I tried to do this:

>> I3=imread('Image.jpg'); >> I2=bwboundaries(I3);

And I am getting error like this:

Error using bwboundaries Expected input number 1, BW, to be two-dimensional.

Error in bwboundaries>parseInputs (line 187) validateattributes(BW_in, {'numeric','logical'}, {'real','2d','nonsparse'}, ...

Error in bwboundaries (line 140) [BW, conn, findHoles] = parseInputs(args{:});

I tried to even convert the image to binary explicitly and then do it, but still I am getting a different error saying the image size is too large to perform the function.

I am trying to do this command window btw, I don't think that might be one of the problem anyway.

If I have to code it myself, can somebody explain how to do it?

Thanks in advance

Answer 1

[Sayan Saha]

Here is an example of using "bwboundaries" to find the inner contours of an image based on the example in the documentation:

https://www.mathworks.com/help/images/ref/bwboundaries.html#bu1wvam-5

I = imread('coins.png');
imshow(I);
BW = imbinarize(I);
[B,L] = bwboundaries(BW,'noholes');
figure;
hold on;
for k=1:length(B)
    boundary = B{k};
    hold on;
    plot(boundary(:,2), boundary(:,1));
end

Following MATLAB Answers post might also be relevant:

https://www.mathworks.com/matlabcentral/answers/168951-outer-and-inner-contour-of-the-image-from-the-centroid