matplotlib-users Mailing List for matplotlib

On Saturday 08 November 2008, John Hunter said something like:
> On Sat, Nov 8, 2008 at 1:02 AM, Joshua J. Kugler 
<jo...@ee...> wrote:
> > On Friday 07 November 2008, John Hunter said something like:
> >
> > http://matplotlib.sourceforge.net/faq/troubleshooting_faq.html#repo
> >rt-a-problem
> >
> > Sorry, I wasn't so much reporting  a problem with matplotlib as I
> > was wondering if I was missing something.  I'll try to extract a
> > free-standing example, but it might be hard...there's a lot of code
> > interacting here.  I'll work on that when I get a chance.
> >
> > Thanks!
>
> The point about making a free standing example is that often there is
> some other problem with your code, and the problem is not in the part
> you are posting or asking about.  And we can't help with the part we
> can't see.  In stripping your example down to a free standing
> example, often you will find the problem goes away. Then you will
> ask: what is different about from free the standing example and my
> real code, and in doing so find the real problem.
<snip>
> By not doing the extra work to make a simple example that we can run,
> you are asking us to do so.
<snip>
> I'm not trying to be snippy, it's just that the matplotlib mailing
> list gets a lot of traffic, and in addition to trying to help you
> with your problems, we are trying to fix bugs, add new features,
> solve platform issues and distribution issues, put out releases, and
> we all have jobs and families.

John (and all):

Thanks for your detailed reply.  I understand the need for a 
free-standing example, and understand why I should do it.  And if/when 
I find a problem, I certainly will do that.  The question I was asking 
was, in effect, "Is there another setting I should try to accomplish 
what I want to do."  I just wanted to know if I was missing something 
in the docs, not so much "Matplotlib isn't working."  I'm going to work 
on the problem some more today (and play around with the date graph 
example you suggested) and see if I can figure out anything.

j

-- 
Joshua Kugler
Part-Time System Admin/Programmer
http://www.eeinternet.com
PGP Key: http://pgp.mit.edu/  ID 0xDB26D7CE

On Sat, Nov 15, 2008 at 3:23 PM, Hrafnkell Pálsson <hr...@hi...> wrote:
>
> Hi
> I haven't managed to save a plot background into buffer to be able to
> restore it later.
> I use matplotlib to draw weather maps (see www.belgingur.is), and though the
> weather constantly changes the outlines of the countries are the same for
> every picture.
> Currently I plot the coastlines anew for every picture, which is kinda *not
> smart*.

Have you tried the "copy from bbox" / "restore_region" methods.  Draw
just what you want to save, and use "copy_from_bbox".  Later when you
want to plot something new, do a "restore_region" onto a clean canvas
and then plot the new stuff on top:

* background = canvas.copy_from_bbox(ax.bbox) - copy the region in
ax.bbox into a pixel buffer and return it in an object type of your
choosing. bbox is a matplotlib BBox instance from the transforms
module. background is not used by the matplotlib frontend, but it
stores it and passes it back to the backend in the restore_region
method. You will probably want to store not only the pixel buffer but
the rectangular region of the canvas from whence it came in the
background object.


* canvas.restore_region(background) - restore the region copied above
to the canvas.


* canvas.blit(bbox) - transfer the pixel buffer in region bounded by
bbox to the canvas.

Search the examples for "copy_from_bbox" on the web site
http://matplotlib.sourceforge.net/search.html

If you are still having troubles, let me know and I can give more help.

JDH