Matlab: How can I find the number of black pixels in a color image?

Use nnz

like this -

nnz(all(im==0,3))

      

        
        
        
      

    

where im

is your image data.

The alternatives are sum(reshape(all(im==0,3),[],1))

and sum(sum(all(im==0,3)))

.

The black pixels are assumed to be triplets (0,0,0)

.

Instead, if you are defining black pixels as pixels that have range values [0 th]

for the same pixel location across all channels, use this -

nnz(all(im<=th,3))