My cell counter is now working with the GPU (and browser, don't know whether those scientific file format works, it should)
and twice as fast as on the CPU alone. Also you (nah, I) can see the progress of counting (CPU | that needs the most time ~90-95%)

For you: my CPU has 2.5GHz, and it needed(incl. GPU) ~25s for these 5124 cells on a 1872 x 2468 pixel source image.

256415434s ago, by Antonio