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February 2010
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2010.02.09 09:11 "Re: FFT on two TIFF images", by <jcupitt@gmail.com>
On 9 February 2010 08:16, Gil, Debora, VF-ES (dgilalv) STU <debora.gil@vodafone.com> wrote: > Thanks Andy and Richard, some other people pointed out the possibility > of using OpenImageIO. It looks good and I'll give it a try. Another possibility might be the vips image processing library (I'm one of the maintainers). It uses libliff and libfftw and has convenient functions for doing various Fourier-domain correlation operations. It has a Python binding, so it's very easy to use. http://www.vips.ecs.soton.ac.uk It's LGPL. The Python binding doesn't currently work on WIndows. It comes with all the major Linux distributions. > So, in the receiving part, I have both, the sent image and the received > image. I want to compare them, to see if the line has caused any error. > Both images are of course the same size. I have several types of images, > some are multipage TIFF. I guess there is no paper involved? If that's the case a very simple solution would be just so subtract the two images and count the non-zeros. You could normalise to the image size and calculate an error rate. In vips python, that would be: ------ #!/usr/bin/python from vipsCC import * a = VImage.VImage ("image1.tif") b = VImage.VImage ("image2.tif") # average absolute difference # vips unpacks 1 bit images to 8 bits 0/255, so divide by that avg = (a.subtract (b)).abs ().avg () / 255 # that'll be very small, so display as errors - per - megapixel print 'errors per million pixels:', avg * 1000000 ---------- John