Simply take the red channel, threshold it, find the area, and if the area is less than some minimum allowable area, alert the user. Try this
rgbImage = imread(filename);
redChannel = rgbImage(:,:,1);
binaryImage = redChannel < 128; % Whatever...
binaryImage = bwareaopen(binaryImage, 100);
labeledImage = bwlabel(binaryImage, 4);
measurements = regionprops(labeledImage, 'Area');
allAreas = [measurements.Area];
minAllowableArea = 500; % Whatever.
for k = 1 : length
fprintf('Area = %d pixels.', allAreas(k));
if allAreas(k) < minAllowableArea
message = sprintf('Blob #%d is too small at %d pixels', k, allAreas(k));
uiwait(warndlg(message));
end
end
That's untested so you might have to tweak it.
