Re: [Matplotlib-users] Change in pcolor functionality from 0.99.1.1 to 1.0.0

[Benjamin R. <ben...@ou...>]

On Mon, Nov 15, 2010 at 4:14 AM, Guy Griffiths
<guy...@re...>wrote:

>
> On Friday 12 Nov 2010 15:20:43 Ryan May wrote:
> > On Fri, Nov 12, 2010 at 8:40 AM, Benjamin Root <ben...@ou...> wrote:
> > > On Fri, Nov 12, 2010 at 5:11 AM, Guy Griffiths
> > > <guy...@re...>
> > >
> > > wrote:
> > >> Hi,
> > >>
> > >> I've been using matplotlib for a while for plotting scientific data,
> and
> > >> recently upgraded from version 0.99.1.1 to 1.0.0.  Primarily I use
> > >> pcolor to
> > >> produce plots of concentration in 2D space.  I use reasonably fine
> > >> meshes, and
> > >> in v0.99.1.1 the output looked great.
> > >>
> > >> In v1.0.0, all of my plots (using the same code) have faint gridlines
> > >> visible.
> > >> Since the mesh I am using is quite fine, this makes the plots look
> > >> terrible
> > >> (i.e. more gridlines than actual data).  This seems to be controlled
> by
> > >> the
> > >> "edgecolors" keyword, but even when set to 'none' they are still
> there.
> > >>  Is
> > >> there any way to remove them completely without reverting back to
> > >> 0.99.1.1 (which I'd prefer not to do, since some of the API changes
> are
> > >> really useful
> > >> for creating very polished graphs suitable for publication)?
> > >>
> > >> imshow seems to have closer results to what I want (i.e. no
> gridlines),
> > >> but
> > >> with imshow, the axes denote the pixel position, and there is no
> option
> > >> to display on polar axes (which is essential).
> > >>
> > >> Any help would be much appreciated.
> > >>
> > >> Regards,
> > >>
> > >> Guy Griffiths
> > >
> > > Guy, I have noticed something similar a few months ago with pcolor, but
> I
> > > am not certain if it is the same problem as yours.  First, which
> backend
> > > are you using?  Second, are you seeing the grid lines in both the
> figure
> > > window and the saved output?  Also, what format are you saving your
> > > output to? Lastly, which pcolor function are you using (pcolor(),
> > > pcolormesh(), pcolorfast())?
> > >
> > > If you could include a screenshot or the saved file, I could see if it
> is
> > > similar to my problem.
> >
> > Yeah, I had noticed a problem with pcolor too. You can see the problem
> > I've been seeing here:
> >
> >
> http://matplotlib.sourceforge.net/examples/pylab_examples/pcolor_demo.html
> >
> > Calling pcolor with antialiased=False removes the lines, but that's
> > just a workaround, not a solution.  I'm not really sure where to start
> > to track this down, so if anyone has a suggestion, I'm all ears.
> >
> > Ryan
>
> Hi,
>
> Thanks for the help.  The problem I'm seeing is as Ryan describes (same
> effect
> as in the screenshot, but let me know if you still want me to provide an
> example), and appears in both the figure window and saved output (at least
> png
> and pdf).  The backend I am using is Qt/Agg.  I was using pcolor(), but it
> appears that pcolormesh() doesn't (always) have this problem.  Setting
> antialiased=False removes some of the problems.  In summary:
>
> pcolor(), antialiased=True - lines on screen, png, pdf
> pcolor(), antialiased=False - lines on pdf, fine on png/screen
> pcolormesh() - lines on pdf, fine on png/screen
>
> Regards,
>
> Guy
>

Guy,

I found my old bug report on this visual artifact.  Oddly enough, the
problem for me was with pcolormesh, not with pcolor.  There is a script
attached to the report that tests 4 combinations of function calls and
rasterized=True.  Could you see how it turns out for you?

Thanks,
Ben Root