[Octave-bug-tracker] [bug #43218] imshear causes more signal spread than expected and inconsistent vertical offset

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?43218>

                 Summary: imshear causes more signal spread than expected and
inconsistent vertical offset
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Sat 13 Sep 2014 04:34:01 PM UTC
                Category: Octave Forge Package
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Inaccurate Result
                  Status: None
             Assigned to: None
         Originator Name: sepesi
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 3.6.4
        Operating System: Microsoft Windows

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Details:

When the argument ALPHA is less than one, I believe the signal spread should
be limited to just one neighboring element. There
also is an unexpected one pixel variance in the sheared image's vertical
offset depending on the image height. Both unexpected results are created on
my system with the following code:


figure(1);

A = zeros(9,5); A(5,:) = 1;
Au = imshear(A,'y',0.5,'crop');
Ad = imshear(A,'y',-0.5,'crop');
subplot(2,3,1), imagesc(A), colorbar, colormap gray, title('unsheared');
subplot(2,3,2), imagesc(Au), colorbar, colormap gray, title('shear up');
subplot(2,3,3), imagesc(Ad), colorbar, colormap gray, title('shear down');

A(1,:) = [];
Au = imshear(A,'y',0.5,'crop');
Ad = imshear(A,'y',-0.5,'crop');
subplot(2,3,4), imagesc(A), colorbar, colormap gray, title('unsheared');
subplot(2,3,5), imagesc(Au), colorbar, colormap gray, title('shear up');
subplot(2,3,6), imagesc(Ad), colorbar, colormap gray, title('shear down');

figure(2);

A(1,:) = [];
Au = imshear(A,'y',0.5,'crop');
Ad = imshear(A,'y',-0.5,'crop');
subplot(2,3,1), imagesc(A), colorbar, colormap gray, title('unsheared');
subplot(2,3,2), imagesc(Au), colorbar, colormap gray, title('shear up');
subplot(2,3,3), imagesc(Ad), colorbar, colormap gray, title('shear down');

A(1,:) = [];
Au = imshear(A,'y',0.5,'crop');
Ad = imshear(A,'y',-0.5,'crop');
subplot(2,3,4), imagesc(A), colorbar, colormap gray, title('unsheared');
subplot(2,3,5), imagesc(Au), colorbar, colormap gray, title('shear up');
subplot(2,3,6), imagesc(Ad), colorbar, colormap gray, title('shear down');






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File Attachments:


-------------------------------------------------------
Date: Sat 13 Sep 2014 04:34:01 PM UTC  Name: bug_imshear1.png  Size: 52kB  
By: None

<http://savannah.gnu.org/bugs/download.php?file_id=32086>
-------------------------------------------------------
Date: Sat 13 Sep 2014 04:34:01 PM UTC  Name: bug_imshear2.png  Size: 47kB  
By: None

<http://savannah.gnu.org/bugs/download.php?file_id=32087>

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  <http://savannah.gnu.org/bugs/?43218>

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