MATLAB: How to find distribution of thickness?

binarydigital image processingimage analysisimage processingImage Processing Toolboximage segmentationplotting

Hi All,

How to find distribution of thickness in black portion of images like this ??

https://plus.google.com/photos/116243239493929305987/albums/5654551980894583617/5695615569581847202?banner=pwa#photos/116243239493929305987/albums/5654551980894583617/5695615569581847202

Thanks in advance Shan

Best Answer

This is how:

1. Use bwdist() to calculate the Euclidean Distance Transform.
2. Use bwmorph() to calculate the skeleton.
3. Get the ridgelines by taking the EDT image at the skeleton locations.  The values along the ridgelines of the EDT will be the distance from the ridgeline (backbone, skeleton) to the background.  You may want to double these values to get the width all the way across instead of only half way across.
4. Take the histogram of those values.

It should only be 4-6 lines of code (not including comments, calls to display and plot things etc.). Give it a shot.

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You forgot to attach your image. Usually when people ask for image processing advice, they attach an image.

I would compute the Euclidean Distance Transform for the binary image with bwdist().

edtImage = bwdist(binaryImage);

Then ask regionprops for the pixel values of the EDT image.

labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, edtImage, 'PixelValues');

If the max pixel value for that ring is acceptable, store that index.

numRings = length(props)
keepers = false(1, numRings)
for k = 1 : numRings
    if max(props(k).PixelValues) > someValue
        % This ring is thick enough.  So keep it.
        keepers(k) = true;
    end
end

Then use ismember(mask, indexes) to extract just the rings that meet your criteria.

filteredBinaryImage = ismember(labeledImage, find(keepers));

The code is just off the top of my head - untested, so you may have to adapt it some. If you want the average thickness of the ring, then you'll have to call bwmorph() to skeletonize it and then multiply the skeleton image by the EDT image to get the thickness just along the centerlines. Then get the mean of all those pixels.

If you need more help, post your image and ring thickness criteria for keeping and excluding rings.

Best Answer

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