Python图像处理耗时太长

I would like to do image processing in Python. The problem is that I have a loop that is recording the image data from a camera into a numpy array, but in the loop I am trying to do a correlation of pixel data from the last image to the current image to determine whether or not I need to do further processing. This however is killing the execution speed of the loop which is showing lagged image output. I would like to do image processing in Python.