Using the Agg renderer by itself

Development matplotlib-devel
1

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

···

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@...236...

2

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.

One more question. I see:

     def draw_markers(self, *kl, **kw):
         # for filtering to work with rastrization, methods needs to be wrapped.
         # maybe there is better way to do it.
         return self._renderer.draw_markers(*kl, **kw)

What do I pass in to this function?

Thanks,
   -Chris

···

On 11/23/11 9:52 AM, Chris.Barker wrote:

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

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@...236...

3

2011/11/23 Chris.Barker <Chris.Barker@...236...>:

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.

http://www.effbot.org/zone/aggdraw-index.htm

http://www.effbot.org/imagingbook/imagedraw.htm

Don't know if this suffices your needs.

Friedrich

4

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

Ben Root

···

On Wednesday, November 23, 2011, Chris.Barker <Chris.Barker@…236…> 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.

  1. 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

5

Hmm -- coll idea -- I'll look into that at some point. However, as I don't need the MPL machinerey, but just the renderer, I'm not sure it would buy me much.

And I'm not sure I can:

a) count on html 5 on all browsers we need to support

or

b) get the drawing performance I want if I have to push all the data to the client to draw.

But something to keep an eye on, thanks.

-Chris

···

On 11/23/11 10:38 AM, Benjamin Root wrote:

On Wednesday, November 23, 2011, Chris.Barker <Chris.Barker@...236... > <mailto:Chris.Barker@…236…>> 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.

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

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@...236...

6

2011/11/23 Chris.Barker<Chris.Barker@...236...>:

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.

http://www.effbot.org/zone/aggdraw-index.htm

I've been wondering about that -- it doesn't look terribly maintained -- no updates for a long time, and I'm concerned about performance 99 if you are drawing something simple, but with lot's of points, all that conversion from numpy types to python type to C types is going to be an issue.

http://www.effbot.org/imagingbook/imagedraw.htm

this is definitely slow for what I'm doing.

Thanks,
   -Chris

···

On 11/23/11 10:13 AM, Friedrich Romstedt wrote:

--
Christopher Barker, Ph.D.
Oceanographer

Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception

Chris.Barker@...236...