How to sum out all the 1 in the bw image?

I got 280x424x3 logical image.

I want to sum out all the 1 in the image. How to do it?

I want to know how many pixel inside the black region in the image.

Answer 1

[Stephen23]

This is my answer to your last question. If X is a grayscale RGB image, this will count the white pixels:

idy = all(X,3);    % R==G==B
out = sum(idy(:)); % count 1's

Note that you should not store your image as a .jpg file, as this is a lossy format. .png would be more suitable.

Anyway, here is one easy way to count the pixels with values less than 127 ("black"):

>> X = imread('1_2.jpg');
>> Y = X>127;
>> L = sum(Y(:)) % Light
L =  97146
>> D = sum(~Y(:)) % Dark
D =  21574

And the total pixels in both of these is equal to the total pixels in the image:

>> L+D
ans =  118720
>> prod(size(X))
ans =  118720

Answer 2

[khan]

use

Total_ones = numel(find(YourMatrix(:)==1)

[DGM]

area = nnz(mask);

is a lot simpler and faster