Re: opengl and images (was: Re: fltk backend fix & mouse wheel scroll factor)

[Shai Ayal]

On Sat, Oct 3, 2009 at 5:30 PM, Shai Ayal <address@hidden> wrote:
> On Sat, Oct 3, 2009 at 4:48 PM, John W. Eaton <address@hidden> wrote:
>> On  3-Oct-2009, Shai Ayal wrote:
>>
>> | On Thu, Oct 1, 2009 at 9:21 PM, John W. Eaton <address@hidden> wrote:
>> | >  image (rand (8, 10, 3))
>> | >  set (gca, 'xlim', [2, 4])
>> | >
>> | > I would expect something like the first image attached below
>> | > (generated with the gnuplot backend), but I get the second.  Oddly,
>> | > the axis is resized to fill the screen if the window is refreshed (by
>> | > placing another window on top of it then uncovering it, for example).
>> | > I'm not sure what the proper fix is.  Any clues?
>> |
>> | I attach a changeset to fix these issues -- It clips the image
>> | according to axes limits. It also fixes the limits of the image object
>> | to take into account the real size of the image
>>
>> I applied the patch, but it still does not seem to behave as I would
>> expect.  Now I see the following after doing
>>
>>  image (rand (8, 10, 3))
>>  set (gca, 'xlim', [2, 4])
>>
>> (first attached figure) when I would expect something more like the
>> gnuplot output (second attached figure).
>>
>> Do you see a way to display the  partial pixels between x=[2,2.5] and
>> x=[3.5,4]?
> No. This a limitation of OpenGL images -- no partial pixels. Do you
> think this is serious enough to warrant a rewrite in terms of another
> OpenGL primitive?
>
>> Also, do you understand what is causing the odd scaling of
>> the axes?  they are adjusted if the figure window is redrawn (for
>> example, but covering it with another window and then uncovering it)?
> I don't get it either.
Maybe it's because image sets axes.xlimmode  and axes.ylimmode to be manual?
If I do
image (rand (8, 10, 3))
set (gca, 'ylimmode', 'auto', 'xlimmode', 'auto')
set (gca, 'xlim', [2, 5])
then it looks as expected.

However, I still don't understand why redrawing the figure corrects this.

Shai