[Octave-bug-tracker] [bug #45372] crash on zoom using imshow with uint8 data (also image and imagesc)

[H. G.]

URL:
  <http://savannah.gnu.org/bugs/?45372>

                 Summary: crash on zoom using imshow with uint8 data (also
image and imagesc)
                 Project: GNU Octave
            Submitted by: hardy
            Submitted on: Mo 22 Jun 2015 10:42:01 GMT
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Crash
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.0.0
        Operating System: Any

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Details:

Here is a little script to show the behavior:


clear, close all;
graphics_toolkit qt

I = uint8(ones(50,50,3));
J = ones(50,50,3);

imshow(I);   % --> crash  (double is OK)

%image(I);   % --> errors (double is OK)
%imagesc(I); % --> errors (double is OK)


To reproduce the crash, do the following few steps:
1. in the figure window, press the zoom button "+Z"
2. use the left mouse button inside the plot region to the select a zoom
region 
3. CRASH, Octave closes

The resulting error messing, when using Octave in CLI mode is:


error: invalid conversion of uint8 matrix to Matrix
error: invalid conversion of uint8 matrix to Matrix
error: octave_base_value::matrix_value(): wrong type argument '<unknown
type>'
error: A(I,J): row index out of bounds; value 1 out of bound 0
terminate called after throwing an instance of 'octave_execution_exception'
panic: Abgebrochen -- stopping myself...
attempting to save variables to 'octave-workspace'...
save to 'octave-workspace' complete


A few observations that might help:
* This happens only with the qt plotting toolkit. Fltk and gnuplot are fine.
* This happens only with integer data (uint8 in the above example). Double
data is fine.
* This happened with the 4.0.0 release. I had the crash on a self compiled
version on Ubuntu 14.04 as well as on the official Windows installer.
* If you use image(I) instead of imshow(I) you get error messages  (wich is a
bug in itself) but no crash.
* If you use imagesc(I) instead if imshow, you get error messages (another bug
in itself) but no crash.

This behavior is very disturbing, because image data very often IS uint8 data
(and not double data). The imread function returns uint8 data normally.





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