PIL patches
Add difference_rms to PIL
This is a patch against the Python Imaging Library Imaging-1.1.6. This add the method ImageChops.difference_rms(im1, im2) which returns a float giving the RMS difference between the two given images. This is about 10 times faster than doing it in Python. This can be used to detect changes in images (motion) or to compare the effect of different image operations. If the two images are exactly equal then difference_rms() will return 0.0. As the images diverge the value returned will increase. It will always be a positive number. In general, the greater the difference between the two images then the greater the RMS difference will be.
To apply the patch and build PIL. Assume that Imaging-1.1.6.tar.gz and Imaging-1.1.6.patch are in the same directory.
tar xzf Imaging-1.1.6.tar.gz cd Imaging-1.1.6 patch -p 1 < Imaging-1.1.6.patch python setup.py install
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