matplotlib-devel Mailing List for matplotlib

Hi all,
I seem to be talking to myself here, but if someone (including myself) 
wants to pick this up in the future, it'll be good to have it in the 
archives.
Christopher Barker wrote:
>> There is also the
>> wx.Image.SetDataBuffer method, which will have the wxImage use the
>> buffer passed in without making a copy, but if the buffer doesn't
>> live as long as the image does it will likely cause a crash.
> 
> This would probably be the easiest way to get top performance at the 
> moment. If we can make the Agg data a buffer, and somehow do the 
> reference counting right so it doesn't get deleted while the wxImage is 
> still around (that may not be hard -- the wxImage has to be converted to 
> a wxBitmap to be drawn anyway)
I've been suing this for another use, and Robin just added an improved 
version of new wx.Image factory function I wrote for just this purpose:
def ImageFromBuffer(width, height, dataBuffer, alphaBuffer=None):
 """
 Creates a `wx.Image` from the data in dataBuffer. The dataBuffer
 parameter must be a Python object that implements the buffer
 interface, such as a string, array, etc. The dataBuffer object is
 expected to contain a series of RGB bytes and be width*height*3
 bytes long. A buffer object can optionally be supplied for the
 image's alpha channel data, and it is expected to be width*height
 bytes long.
 A reference to the data and alpha buffer objects are kept with the
 wx.Image, so that they won't get deleted until after the wx.Image
 is deleted. However please be aware that it is not guaranteed that
 an object won't move its memory buffer to a new location when it
 needs to resize its contents. If that happens then the wx.Image
 will end up referring to an invalid memory location and could cause
 the application to crash. Therefore care should be taken to not
 manipulate the objects used for the data and alpha buffers in a
 way that would cause them to change size.
 """
 image = wx.EmptyImage(width, height)
 image.SetDataBuffer(dataBuffer)
 if alphaBuffer is not None:
 image.SetAlphaBuffer(alphaBuffer)
 image._buffer = dataBuffer
 image._alpha = alphaBuffer
 return image
Does the aggDrawer already implement a Python buffer object? If so, 
using this would be easy. If not, then it probably should, unless we go 
straight to the numpy array protocol.
-Chris
-- 
Christopher Barker, Ph.D.
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