I'm trying to generate plots as textures for use within a real-time
graphics application (written using the pythonOgre graphics engine).
I'm brand new to matplotlib so please bear with me. Two questions, one
easy, one possibly hard.
In the following code snippet, I create and draw a pie chart, do some
intermediate work, update the pie fractions, and redraw. I end up with
the second version superimposed on the first. Initially I thought it
was simply a matter of clearing the canvas, but as I repeat this test
with more and more updates, the redraw seems to slow down - this makes
me think that each redraw is actually rerendering all the layers. Is
this the case? If so, how do I avoid it?
# create matplotlib figure
figure = Figure(figsize=(4,3), dpi=200, frameon=True)
figureCanvas = FigureCanvas(figure)
# unchanging details of pie chart
ax = figure.add_subplot(111) # pie plot
labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
ax.set_title('Example pyOgre Pie Chart')
ax.grid(True)
ax.pie([25,25,30,20], labels=labels)
figureCanvas.draw()
# ....
# update pie chart
ax.pie([30,25,25,20], labels=labels)
# matplotlib draw
figureCanvas.draw()
And the harder question. I need access to the address of the raw image
buffer. (I assume this is a contiguous block of c-allocated memory?)
Presently, I copy into a ctypes buffer but this slows things down
significantly. Is there an alternative approach?
# retrieve buffer from matplotlib
height = int( figureCanvas.get_renderer().height )
width = int( figureCanvas.get_renderer().width )
# extract image buffer (need as void ptr to contiguous byte array)
buff = figureCanvas.buffer_rgba(0,0)
cbuffer[:] = buff[:] ## would prefer to eliminate this step
address = ctypes.addressof(cbuffer)
Any help is much appreciated ...
Cheers,
Darran.
--
Darran Edmundson [EMAIL PROTECTED]
http://www.edmstudio.com
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