|
From: | Journeaux, Ian |
Subject: | imrotate: Differences between Matlab and Octabe |
Date: | Mon, 15 Mar 2010 09:17:17 -0500 |
In answer to one of my
previous question, someone pointed out that the default settings for imrotate
were different for Matlab (“nearest”) and Octave (“bilinear”).
That was an oversight on our part but as we have dug in a little more, using
the “nearest” procedure, there are still small differences between
Matlab and Octave. We cut a 200 x 200 pixel
image around a feature in one of our samples. We then did a rotation on the image
by writing a small Matlab / Octave program, that we ran on both platforms with
the 3 (bilinear, bicubic, nearest) techniques, giving 6 results. For our purposes, we were
mainly interested in the nearest procedure as we want to minimize smoothing of
the pixel values in the images. We observed that the nearest
versions of Matlab and Octave are not quite the same producing small
differences in the results. About half (roughly) of Matlab pixels are 1 grey
level above that of Octave, the rest being equal. This suggests a different way
of rounding. The central pixel (100,100) where the major shift occurs there is
a much larger difference - 8 grey levels. In all cases Matlab grey levels are
exactly where they should be wrt the original image. The results for “nearest” are probably good
enough for us but since we had dug into it, and observed some differences, I
though we should share the results. Ian Journeaux Manager – Process Technology Phone:
(715)
422-2203
Fax:
(715) 422-2227 E-Mail: address@hidden This electronic message contains information from NewPage Corporation or subsidiary companies, which may be confidential, privileged or otherwise protected from disclosure. The information is intended to be used solely by the recipient(s) named. If you are not an intended recipient, be aware that any review, disclosure, copying, distribution or use of this transmission or its contents is prohibited. If you have received this transmission in error, please notify NewPage immediately at address@hidden |
Rotationtests.zip
Description: Rotationtests.zip
[Prev in Thread] | Current Thread | [Next in Thread] |