how can i obtain the final result after roipoly?
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hello
i have agrayscale image
i want to extract my target roi
so i wrote this
m=imread(.....); BW=roipoly(m);
after that how can i obtain the roi filling with grayscale ? i mean how can i make benefit of the polygon that i obtained in BW to get my roi as agrayscale?
thanks
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Accepted Answer
David Young
on 18 Jan 2012
If you want to have an image that only shows the original grayscale within the polygon, you can use
mnew = m .* cast(BW, class(m));
EDIT Added in response to comment
If you wish to extract the part of the image containing the region, you can do it like this:
BWprops = regionprops(BW, 'BoundingBox');
smallim = imcrop(mnew, BWprops.BoundingBox);
You can then position smallim in the figure, or copy it into the centre of a larger array.
7 Comments
David Young
on 19 Jan 2012
You can find the CoG of the ROI using the 'Centroid' option in regionprops. You could get both the bounding box and the centroid in the same call to regionprops.
You can copy the small region into the middle of a larger array by assigning it to a particular range of indices, as in
bigarray(rowstart:rowend, colstart:colend) = smallarray;
The problem is then working out values for rowstart etc., but you should find that reasonably straightforward.
Alternatively, you can use padarray to put a border of zeros round the small image.
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