Faster way to loop through every pixel of an image in Python?

Question

I need to loop through each pixel of a 2560x2160 2D numpy array (image). A simplified version of my problem is as follows:

import time
import numpy as np

t = time.clock()
limit = 9000
for (x,y), pixel in np.ndenumerate(image):
    if( pixel > limit )
        pass
tt = time.clock()
print tt-t

This is taking an obnoxious ~30 seconds to complete on my computer. ( Core i7, 8GB ram ) Is there a faster way to perform this loop with an interior 'if' statement? I am only interested in pixels above a certain limit, but I do need their (x,y) indices and value.

Answer 1

Use a boolean matrix:

x, y = (image > limit).nonzero()
vals = image[x, y]