counting holes in an image

writing an algorithm that will count the number of holes in the image that do not touch the border

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

Answer 1

[Image Analyst]

Threshold then call imclearborder() and bwlabel(). Assuming you have dark holes on a bright background:

% Binarize:
binaryImage = grayImage < someValue;
% Remove those touching border
binaryImage = imclearborder(binaryImage);
% Count holes:
[~, numHoles] = bwlabel(binaryImage);

Answer 2

[Walter Roberson]

Invert the image so the holes become solid and the solid gets removed. Remove from that all solid touching the border -- those correspond to holes that were touching the border in the original. Now count the number of solid objects remaining, and that will be the number of holes in the original.