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[Octave-bug-tracker] [bug #44830] image package: imtransform gives diffe


From: Pantxo Diribarne
Subject: [Octave-bug-tracker] [bug #44830] image package: imtransform gives different numbers on simple rotation
Date: Thu, 14 May 2015 13:38:24 +0000
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:37.0) Gecko/20100101 Firefox/37.0

Update of bug #44830 (project octave):

                  Status:                    None => In Progress            

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Follow-up Comment #10:

Hi,

I attached a new patch that also fixes x/ydata shape (see comment #8) and
add/fix some tests. 

The reason why the output pixel data are not symetric is due to the actual
x/ydata that are computed [1]: as the output image size has to be integer, the
actual (returned) x/ydata have to be recomputed. As specified in Matlab
documentation, x/ydata are not recomputed symetrically, only the second
element of each is altered. To be clear: the output pixels coordinates are
shifted right/down (with regards to the expected center of the image) as
needed.

Now about your interpretation of the fact that boundary pixels are wrong in
Octave, I think you are right but I don't know how to implement this without a
drastic performance drop.

[1] See "xdata" output documentation in
http://fr.mathworks.com/help/images/ref/imtransform.html

(file #34009)
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Additional Item Attachment:

File name: fix_xyscale.patch              Size:5 KB


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Reply to this item at:

  <http://savannah.gnu.org/bugs/?44830>

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