Re: [matplotlib-devel] Using the Agg renderer by itself

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

On Wednesday, November 23, 2011, Chris.Barker <Chr...@no...> wrote:
> Hi Folks,
>
> I've got some drawing to do (for a web app). I don't need all the MPL
> machinery, but I do need a high quality, fast, renderer.
>
> Other options:
>
>  - The python bindings to GD seem to not really being maintained
>
>  - PyCairo is a pain to install, and not fast for Python (doesn't know
> about numpy arrays of points, for instance)
>
>  - Kiva appears to be quite enmeshed with ETS, and thus a bit of trick
> to install (at least without EPD or PythonXY or something)
>
>
> So I thought I'd give MPL's AGG wrappers a try. I've managed to get
> things working, but I do have a couple questions:
>
> 1) are there docs somewhere? What I've found is very sparse, and doc
> strings are minimal -- though I've got the source, so only so much or a
> complaint.
>
> 2) It looks like the AGG renderers take floats for almost everything --
> makes sense, with anti-aliasing and sub-pixel rendering. But is it
> float32 or float64 internally? It seems either will work, but I'm going
> for maximum performance, so I'd like to use the native format.
>
>
> Testing drawing a polygon, I'm a bit confused about GraphicsContext vs
> the renderer. If I do:
>
> gc = GraphicsContextBase()
> transform = Affine2D() # default unit transform
>
> ## draw the polygon:
> ## create a path for a polygon:
> points =
np.array(((10,10),(10,190),(150,100),(290,10),(10,10)),np.float64)
>
> p = Path(points)
>
> gc.set_linewidth(4)
> gc.set_alpha(0.75)
>
> fill_color = (0.0, 1.0, 0.0)
> line_color = (1.0, 0.0, 0.0)
>
> #gc._rgb = line_color
> gc.set_foreground(line_color)
>
> Canvas.draw_path(gc, p, transform, fill_color)
>
> I get a green polygon with a red border, like I'd expect. However:
>
> Why is the outline color set in the GraphicsContext, but the fill color
> passed in to the draw_path call? Or am I doing that wrong?
>
>
> Thanks for input,
>
> -Chris
>
>

There is an HTML5 backend, supposedly.  Don't know how well documented it
is, though.

Ben Root