Re: [Matplotlib-users] export of a specific zone of a figure

[Nicolas <nic...@ya...>]

Thank you very much.
I know very little about numpy in fact.

If I don't find a pure matplotlib method, I will use your suggestion with
wx.
I think however matplotlib may be used only (and it will be even better as I
plan to make a Qt version in the future)

So, in :
>>> from matplotlib.transforms import Value
>>> from matplotlib.backends.backend_agg import RendererAgg
>>> r = RendererAgg(50, 50, Value(72))
>>> r.draw_image(0, 0, im)

What is the correct format for im ?

Thanks,

Nicolas

On 7/2/07, Christopher Barker <Chr...@no...> wrote:
>
> I don't know how to do it with the MPL agg back-end, but I think you
> mentioned wx, and you can do it there instead. a wxImage can be
> constructed from a buffer object, then saved as a PNG. You may need to
> set the rgb and alpha portions separately. See the wxPython wiki and
> search for "Image".
>
> Also:
>
> >             matrix = []
> >             buffer = self.get_renderer().tostring_argb()
> >             l, h = self.GetSize()
> >             for ligne in xrange(h):
> >                 matrix.append([])
> >                 for colonne in xrange(l):
> >                     i = 4*(ligne*h + colonne)
> >                     pixel = buffer[i:i+4]
> >                     matrix[-1].append(pixel)
>
> This is a very slow way to create the numpy array!
>
> Option a: first create an empty array:
>
> matrix = numpy.empty((l,h,4), numpy.byte)
>
> then fill that in. but even better:
>
> you can build the array directly from the buffer string:
>
> matrix = numpy.fromstring(buffer, dtype=numpy.byte)
> lotlib-users
>
> --
> Christopher Barker, Ph.D.
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