I knew of matplotlib, but I was not aware of the GridSpec feature.
Thanks for pointing it out. I'll look into it. Thanks also for your
other comments.
kj
On Nov 4, 1:26 pm, Jason Grout <jason-s...@creativetrax.com> wrote:
> On 11/4/10 11:59 AM, kj wrote:
>
>
>
>
>
> > I would like to extend Sage to allow for recursive composition of
> > graphics arrays. (I.e. to enable having graphics arrays as individual
> > elements in a larger graphics array; as far as I can tell, Sage's
> > graphics_array does not support such higher-order graphics arrays.)
>
> > For this, the function that generates the graphics array must take a
> > 1d or 2d array of graphics objects as one of its arguments, and return
> > a graphics object.
>
> > In order to do this, it would be helpful for me to understand Sage's
> > "data model" for graphics. In particular, I need to determine if
> > Sage's graphics objects are cleanly separate from possible display
> > channels.
>
> > To see why, consider, for example, Mathematica Graphics objects, which
> > are at the center of its graphics model. As far as I can tell from
> > Mathematica's documentation, to the user, such a Graphics object can
> > be interpreted (as a first approximation at least) as nothing more
> > than an abstract textual representation of a graphic, independent of
> > any display channel. This textual representation can be interpreted
> > by various drivers to produced various types of output (e.g. a screen
> > display or PostScript). The key point is that there appears to be a
> > clean separation between Mathematica's Graphics objects, and the
> > channels used for displaying them. (I repeat that all of this is
> > nothing more than a guess on my part, since Mathematica is a black
> > box.)
>
> > This separation of the abstract Graphics objects from any concrete
> > display channel greatly simplifies the problem of creating composite
> > Graphics objects from other Graphics objects, since there's no need to
> > reconcile any possible differences that may exist in channel
> > information for the individual components.
>
> > Is there a similar separation between the specification of Sage
> > graphics objects and display channels? To put it differently, how
> > much information about display channels is encoded in these objects?
> > Is there a write-up (or just some descriptive UML) on Sage's graphics
> > model that discusses these topics?
>
> Yes, there is that separation that you describe. Graphics objects are
> just python objects that know how to draw themselves when asked. They
> draw themselves using matplotlib (see the _render_on_subplot function in
> each object, for exampe, in devel/sage/sage/plot/circle.py). Matplotlib
> then takes care of the "channel," as you call it, or drawing "backend,"
> as matplotlib calls it. That drawing does not happen until the object is
> drawn to an actual file. You can see this since, for example, you can
> save a graphics object as a png file or a pdf file (two different channels):
>
> sage: a=circle((0,0),1)
> sage: a
>
> sage: a.save('test.png')
> sage: a.save('test.pdf')
>
> You can see the save method code in the devel/sage/sage/plot/plot.py.
> Basically, a matplotlib object is created, and then each object is asked
> to draw itself on the canvas (or "axes," in matplotlib terminology).
>
> I think to do what you want, it would be best to understand the
> matplotlib model for drawing multiple figures on an image. Matplotlib
> is the underlying library we use to draw Sage 2d figures, and is very
> powerful. Recently, some new capabilities for drawing arrays of
> graphics have been added (in matplotlib 1.0.0). Here are some links to
> documentation:
>
> http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pypl...
>
> http://matplotlib.sourceforge.net/users/whats_new.html#sophisticated-...
>
> http://matplotlib.sourceforge.net/users/gridspec.html#gridspec-guide
>
> In
> particular,http://matplotlib.sourceforge.net/users/gridspec.html#gridspec-using-...
> describes how to nest arrays of arrays in matplotlib.
>
> I think we just need to wrap and expose this functionality that is
> already in matplotlib in the Sage interface.
>
> Thanks,
>
> Jason
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