[Octave-bug-tracker] [bug #49130] uint8 images are not shown correctly by imshow with gnuplot

[anonymous]

URL:
  <http://savannah.gnu.org/bugs/?49130>

                 Summary: uint8 images are not shown correctly by imshow with
gnuplot
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Mon 19 Sep 2016 05:53:48 PM UTC
                Category: Plotting with gnuplot
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: R.S.Carmenes
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.2.0-rc1
        Operating System: GNU/Linux

    _______________________________________________________

Details:

this code:

graphics_toolkit gnuplot
I=imread('anyimage.png');
imshow(I)

shows a black image if 'anyimage.png' is B&W; and if it is RGB, you can see
the image but with intensities 4-5 times higher than expected.

imshow(I,[]) has no effect whatsoever
imagesc(I) has the same problem

However, if the variable is transformed to double, the image is shown as
expected, and the following three examples do work as expected:

imshow(double(I),[])
imshow(double(I)/255)
imagesc(double(I)/255)

Using octave 4.2.0-rc1 current as today Sep-19, with latest stable gnuplot
(5.0.4). Octave 4.0.3 is ok with this gnupolot; this problem doesn't appear
with graphics_toolkit fltk or qt. 




    _______________________________________________________

Reply to this item at:

  <http://savannah.gnu.org/bugs/?49130>

_______________________________________________
  Message sent via/by Savannah
  http://savannah.gnu.org/