Hi, What is the best way to rasterize a figure into a numpy array for further image processing? The code I have below works, but I am wondering if there is a more convenient way.
Thanks in advance, Geoff
import pylab, numpy
fig = pylab.figure()
pylab.plot( [1, 2, 1] )
dpi = fig.get_dpi()
size = fig.get_size_inches()
shape = size[1] * dpi, size[0] * dpi, 3
image = fig.canvas.renderer.tostring_rgb()
image = numpy.fromstring( image, 'u1' ).reshape( shape )
pylab.imshow( image )
Geoffrey Ely wrote:
Hi, What is the best way to rasterize a figure into a numpy array for further image processing?
untested, but I suspect:
image = numpy.frombuffer( fig.canvas.renderer.buffer_rgba).reshape( shape )
might work -- something like that, anyway.
-CHB
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Thanks for the help. With that I get:
AttributeError: 'function' object has no attribute '__buffer__'
I found a cleaner way to get the shape, so this is getting better:
shape = fig.canvas.get_width_height()[::-1] + (3,)
image = numpy.fromstring( fig.canvas.renderer.tostring_rgb(), 'u1' ).reshape( shape )
-Geoff
On Nov 12, 2009, at 2:01 PM, Christopher Barker wrote:
Geoffrey Ely wrote:
Hi, What is the best way to rasterize a figure into a numpy array for
further image processing?untested, but I suspect:
image = numpy.frombuffer( fig.canvas.renderer.buffer_rgba).reshape( shape )
shape = fig.canvas.get_width_height()[::-1] + (4,)
im = np.frombuffer(fig.canvas.buffer_rgba(0,0),
dtype=np.uint8).reshape(shape)
Using buffer_rgba is more efficient than using tostring_rgb as no
memory is allocated. But, I believe that "im" is a read-only "view" of
the canvas. So, you must make a copy if you want to show it with
imshow as in your original code.
If you're using PIL,
import PIL.Image
im2=PIL.Image.frombuffer("RGBA", fig.canvas.get_width_height(),
fig.canvas.buffer_rgba(0,0), "raw", "RGBA", 0, 1)
Regards,
-JJ
On Thu, Nov 12, 2009 at 6:32 PM, Geoffrey Ely <gely@...1887...> wrote:
Thanks for the help. With that I get:
AttributeError: 'function' object has no attribute '__buffer__'
Work perfectly. Thanks, JJ!
-Geoff
On Nov 12, 2009, at 4:32 PM, Jae-Joon Lee wrote:
shape = fig.canvas.get_width_height()[::-1] + (4,)
im = np.frombuffer(fig.canvas.buffer_rgba(0,0),
dtype=np.uint8).reshape(shape)Using buffer_rgba is more efficient than using tostring_rgb as no
memory is allocated. But, I believe that "im" is a read-only "view" of
the canvas. So, you must make a copy if you want to show it with
imshow as in your original code.If you're using PIL,
import PIL.Image
im2=PIL.Image.frombuffer("RGBA", fig.canvas.get_width_height(),
fig.canvas.buffer_rgba(0,0), "raw", "RGBA", 0, 1)