Legacy ImageMagick Discussions Archive

Is this a bug or some feature (of miff) that I do not understand? Why do I not get identical results (rmse = 0). I believe that the miff is the one in error from other tests with one of my scripts. This is a subset of 5 command lines that I had performed separately saving as 1) mpc, or 2) miff or 3) all in one command line. The mpc results match the all in one command line results. This is the first command that did not match in the sequence of 5 commands.


convert -version
Version: ImageMagick 6.8.9-2 Q16 x86_64 2014-05-30 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules
Delegates: bzlib cairo fftw fontconfig freetype gslib jbig jng jp2 jpeg lcms lqr ltdl lzma openexr png ps rsvg tiff webp x xml zlib

This does not appear to be fixed in 6.8.9.3 Q16 Mac OSX. I now get the following, which is not 0 as it should be, but different from above.

convert rose: -colorspace HSI -set colorspace sRGB rose.mpc
convert rose: -colorspace HSI -set colorspace sRGB rose.miff
compare -metric rmse rose.mpc rose.miff null:
75.6441 (0.00115426)

MPC is saved to the quantum depth of the ImageMagick executable, whereas any other format is typically saved at the same depth as the input image. In your example, MPC is 16-bit whereas MIFF is 8-bit thus the non-zero RMSE is expected. To get a 0 RMSE, simply add -depth 16 to your command line.

Thanks for the explanation. That does indeed fix the issue.