How to find object perimeter/bounding box perimeter?

Can some one please provide me a code that finds a ratio between object perimeter and bounding box perimeter:

ratio = object perimeter / bounding box perimeter

[KSSV]

What data you have?

[Dominic]

I have five blobs in a binary image.

Now i want to divide the perimeter of blobs by their corresponding bounding box perimeter.

Answer 1

[Image Analyst]

See https://www.mathworks.com/matlabcentral/answers/165038-circularity-of-an-image#answer_161171

[Dominic]

Sir, is it possible to get perimeter of all bounding box??

The link you have shared, that is for circularity. But how i could find all the perimeter of all blobs in a binary image?

And how to divide the perimeter of blobs by their corresponding bounding box perimeter?

[Image Analyst]

Use regionprops to get the bounding boxes, then add the widths and heights

props = regionprops(labeledImage, 'BoundingBox');
bb = [props.BoundingBox];
widths = bb(3:4:end);
heights = bb(4:4:end);
bbPerimeters = 2 * (widths + heights);

bbPerimeters is the perimeter of all the boxes. Each index is the perimeter of one of the blob's bounding boxes.

[Dominic]

Thank you very much, Sir.

That's exactly the method which was i looked for.

Thank you again.

[sana trimeche]

the widths = X max - X Min then widths= bb(3:4:end)- bb(1:4:end); NO ?

[Image Analyst]

No. Why do you think bb(3) is the x max value? You can tell whomever told you that, that they're wrong because you and I can both read regionprops and see that "the vector [ul_corner width], ul_corner specifies the upper-left corner of the bounding box in the form [x y z ...]. width specifies the width of the bounding box along each dimension in the form [x_width y_width ...]"

So bb is [xLeft, yTop, xWidth, yHeight].