Jerry Hill wrote: > Hello all, > > I have a piece of code I could use some help optimizing. What I'm > attempting to do is periodically grab a screenshot, and search for 2D > patterns of black pixels in it. I don't care about any color other > than black. Here's some simple code that simulates my worst-case > scenario, scanning the whole screen for a sequence that does not > exist: > > import ImageGrab # From the PIL library > > def removeColor(rgb): > r, g, b = rgb > return (r == 0 and g == 0 and b == 0) > > BMP = ImageGrab.grab.getdata() > x = map(removeColor, BMP) > > The idea is to search for sequences of black pixels on a background > that can change colors. To that end, I transform the screengrab into > a sequence of either black or nonblack pixels as I search them. Note > that in my actual code, I use imap so I only transform pixels as I > search them, and I'm using the KnuthMorrisPratt algorithm from > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/117214 to do > the actual searching. > >> From some testing using the timeit module: > > map(None, BMP) takes about 0.6 seconds on a 1600x1200 screengrab. > map(removeColor, BMP) takes about 1.5 seconds. > > I'd love to speed things up, if possible. It seems like what I'm > doing would probably be a fairly well defined problem, but I don't > know enough about the field to even know where to start my research, > so even a list of keywords that would point me to discussion of > similar topics would be welcome. > > This is being done in Python 2.5c2 using PIL 1.1.5 > Use PIL for grabbing the screenshot and numarray for processing the image. See http://groups.google.com.vc/group/comp.lang.python/browse_thread/thread/6207e7526fb6fdc6/a05646969d59102e for some further helpful hints towards speeding things up.
Claudio Grondi -- http://mail.python.org/mailman/listinfo/python-list
