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

[Christopher B. <Chr...@no...>]

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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Chr...@no...