Faster way to extract histogram from an image

Question

I\'m looking for a faster way to extract histogram data from an image. I\'m currently using this piece of code that needs about 1200ms for a 6mpx JPEG image:

Answer 1

You can use getSamples(int x, int y, int w, int h, int b, double[] dArray) method It's possible that this method have internal optimisations. Also, you can try to swap width and height.

for (int i = 0; i < width; i++) 
   for (int j = 0; j < height; j++) {
   }
}

And

for (int i = 0; i < height; i++) 
   for (int j = 0; j < width; j++) {
   }
}

Between this two variants performance difference will be huge. This is influence of the cpu cache