MATLAB: I have a 512x512x3 grey scale image. i want to count the number of pixel with intensities ranging between 140 – 200 and 0 – 30. how can i do that

Question

i converted the image initially using the rbg2gray command. following that i created a mask. What command should i use to count all values in the mask that have non 0 values?

FirstImage = imread('image1.jpeg');
A = rgb2gray (FirstImage);
mask = A > 140 & A < 200;

Answer 1

You can use nnz() - the function to count the number of non-zeros function in an array:

numberOfNonZeros = nnz(A);

Or you can use sum():

numberOfNonZeros = sum(A(:));