MATLAB: Why does bwperim make the border WHITE?!!

borderbwperimImage Processing Toolbox

I want to use bwperim to calculate the perimeter of an object, but I got a strange thing!

I use bwperim in two different states: first to the original binary image and second to its inverse, i.e.,:

%%binaryImage
perim1 = bwperim (binaryImage);
perim2 = bwperim (~binaryImage);

The strange thing is that the first one (perim1) gives an image that is almost black (except the detected boundaries, of course), but:

Exactly, the borders of the whole image, I mean the FIRST row and column and the LAST row and column are white! I mean it has given the value of 1 to the pixels of the image border! Why?!!

For the second one (perim2), this is not the case and it is correct as the original image.

The binary image:

perim1 (with white border):

perim2:

Thanks so much!

Steven

Best Answer

I don't think perim1 should have the edges of the image as white. Can you post the binary image so I can check it out?

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You have white stuff around the border of the image, which means that everything will get filled. So call imclearborder first

binaryImage = imclearborder(binaryImage);
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If you need to put the white border back, let me know.

Best Answer

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