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how to count pixel in binary image ?

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ayrie
ayrie 2014-8-19
评论： Image Analyst 2021-2-27
Hi, i'm trying to counting a binary image on handwritting. how to count a high string using pixel? example for counting high of alphabet A.

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Image Analyst
Image Analyst 2014-8-19
To get the number of pixels in the entire image
numberOfPixels = numel(binaryImage);
To get the number of white/1/true pixels only , and NOT the number of black/0/false pixels:
numberOfTruePixels = sum(binaryImage(:));
  2 个评论
sofia cirne
sofia cirne 2017-6-22
Hello! im doing the same thing apresented above and i used your code to count the black picels and the total number of pixels, but when i submit a completly black image, the number of black pixels is different from the total. Can you help me please?
Image Analyst
Image Analyst 2017-6-22
Bizarre. Of course my code does not count black pixels but I assume you made the obvious alterations (but maybe not). What do you get for this example:
blackImage = false(240, 320);
numberOfPixels = numel(blackImage)
numberOfBlackPixels = sum(~blackImage(:))
The two numbers should be identical.
To know what you're doing wrong, I'll have to see what you're doing, because, as I've said, you're not doing what I posted because I did not post code to count black pixels.

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Asad Alam
Asad Alam 2021-2-25
How can we count pixels of an image by satisfy a condition?
  1 个评论
Image Analyst
Image Analyst 2021-2-27
You can use length() and pass your condition in as a mask. Like if your condition is the pixel value is less than 100, you'd do
condition = yourImage < 100; % tru or false values - a logical 2-d matrix.
pixelsLessThan100 = yourImage(condition); % These are a list (1-d vector) of gray level values.
% Count the number of pixels.
count = length(pixelsLessThan100);

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