How to plot an intensity profile within given pix depth?

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Jakub 2013-7-15

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Hi guys,

Would someone please help me to do the following thing: I have an image of a roughly elliptical object. I know the outline coordinates of it. I would like to:

Plot as a heat-map only pixels of this object that are 10 pixels or so from the object outline inward.
Average the intensities of these 10 pixels at every position and plot this as a heat-map.
Plot #2 on a perimeter of a circle starting from the default position.

The idea is to make an intensity profile within the given depth from the object outline (#1 and #2) and to find the angular distribution of intensities; on X axis angle, on Y axis pix intensities.

Thanks in advance, jakub

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Image Analyst 2013-7-15

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You can the the pixels 10 out from your boundary by getting a binary image from your coordinates first using poly2mask. Then use imdilate to grow that blob out by 10 pixels. Then use bwperim() to get the new boundary locations' pixel values (Untested)

binaryImage = poly2mask(x, y, rows, columns);
SE = strel('disk', R, N)
biggerBlob = imdilate(binaryImage, SE);
perimPixels = bwperim(biggerBlob)
meanGL = mean(grayImage(perimPixels));

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Image Analyst 2013-7-16

To move inward you use imerode(). To move outward use imdilate(). Then use bwperim to get a mask of the outer layer of pixels and logical indexing like I showed you to get the mean value along that outer layer of pixels.

Jakub 2013-7-16

I understand but in that case I will get one mean value for each pixel layer. What I was thinking is to "linearize"the outer layer of pixels then do the same moving inward. something like an intensity profile. For example, for moving 5 pix in depth I will end up with 5 rows of pixels of a length of the perimeter for given pix layer. The rows will be of different length due to the difference in perimeter between outer and inner layer of pixels. Is there a way to interpolate the shorter pix rows to the length of outer pix layer?

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