I also tried using bwlabeln. But how can I remove (i.e. make = 0) those pixels which repeat between 20 to 70 times?
doubt regarding bwconncomp example.
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This is a small doubt.....I'm stuck in the second example given for bwconncomp by Mathworks. This example removes the group of pixels having largest pixels connected (in an 8 connected neighbourhood):
BW = imread('text.png');
imshow(BW);
CC = bwconncomp(BW);
numPixels = cellfun(@numel,CC.PixelIdxList);
[biggest,idx] = max(numPixels);
BW(CC.PixelIdxList{idx}) = 0;
figure, imshow(BW);
I want to change the code to erase groups of pixels which have between 20 to 70 connected pixels (in their 8 connected neighbourhood). How can I do this?
If I do:
idx = numPixels < 70;
I get an error saying : " Maximum variable size allowed by the program is exceeded."
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Walter Roberson
2015-8-28
It looks like you are trying to find a maximum, but it is not clear what you are trying to find a maximum of.
idx = 20 <= numPixels & numPixels <= 70;
valididx = find(idx);
validsizes = numPixels(idx);
if isempty(valididx)
lastvalid = [];
else
lastvalid = valididx(end);
end
[sizelargest, idxlargest] = max(validsizes);
ccidxlargest = valididx(idxlargest);
lastvalid would be for the case where you want to find the index (into CC) of the last cluster that is in the size range -- the maximum being taken over the indices
ccidxlargest would be for the case whee you want to find the index (into CC) of the largest cluster that is left after you isolate down to that range of sizes -- the maximum being taken over the remaining sizes.
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Image Analyst
2015-8-22
Use bwareafilt instead.
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Image Analyst
2015-8-29
If you want to " want to remove the groups of all those points ("remove" i.e., make them = NaN) which have lesser than N (say, 100) points connected to it (in a 26-connectivity neighbourhood)." then the function you want to use is definitely 100% bwareaopen(). It's meant for exactly that. No need to get PixelIdxList at all.
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Walter Roberson
2015-8-28
N = 100;
a = imread('text.png');
c = a;
c(~isfinite(c)) = 0;
BW = logical(c);
CC = bwconncomp(BW);
numPixels = cellfun(@numel,CC.PixelIdxList);
idx = numPixels < N;
unwantedCC = CC(idx);
unwantedpixels = vertcat(unwantedCC.PixelIdxList);
b = a;
b(unwantedpixels) = NaN;
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