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Change {FigureCanvasAgg,RendererAgg}.buffer_rgba to return a memoryview. #11735

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Merged
QuLogic merged 2 commits into from
Dec 27, 2018
Merged

Change {FigureCanvasAgg,RendererAgg}.buffer_rgba to return a memoryview. #11735

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54cd9ce
Change {FigureCanvasAgg,RendererAgg}.buffer_rgba to return a memoryview.
anntzer Jul 22, 2018
5c16eca
Use numpy.take instead of C-level manipulations for tostring_argb etc.
anntzer Jul 23, 2018
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Change {FigureCanvasAgg,RendererAgg}.buffer_rgba to return a memoryview. 
The `buffer_rgba` method now allows direct access to the renderer's
underlying buffer (as a `(m, n, 4)`-shape memoryview) rather than
copying the data to a new bytestring.  This is consistent with the
behavior on Py2, where a buffer object was returned.

While this is technically a backwards-incompatible change, memoryviews
are in fact quite compatible with bytes for most uses, and I'd argue
that the bigger compatibility break was the change from no-copy in Py2
to copy in Py3 (after all that's the main point of the method...).
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@anntzer
anntzer committed Aug 19, 2018
commit 54cd9ceeac50d2a986c86a1c98cc67113dc73381
7 changes: 7 additions & 0 deletions doc/api/next_api_changes/2018-07-22-AL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
`FigureCanvasAgg.buffer_rgba` and `RendererAgg.buffer_rgba` now return a memoryview
```````````````````````````````````````````````````````````````````````````````````

The ``buffer_rgba`` method now allows direct access to the renderer's
underlying buffer (as a ``(m, n, 4)``-shape memoryview) rather than copying the
data to a new bytestring. This is consistent with the behavior on Py2, where a
buffer object was returned.
2 changes: 1 addition & 1 deletion examples/misc/agg_buffer_to_array.py
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Expand Up @@ -15,7 +15,7 @@
fig.canvas.draw()

# grab the pixel buffer and dump it into a numpy array
X = np.array(fig.canvas.renderer._renderer)
X = np.array(fig.canvas.renderer.buffer_rgba())

@pelson pelson Dec 19, 2018

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Wowzers. Good catch.


# now display the array X as an Axes in a new figure
fig2 = plt.figure()
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17 changes: 8 additions & 9 deletions lib/matplotlib/backends/backend_agg.py
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Expand Up @@ -272,7 +272,7 @@ def tostring_argb(self):
return self._renderer.tostring_argb()

def buffer_rgba(self):
return self._renderer.buffer_rgba()
return memoryview(self._renderer)

def clear(self):
self._renderer.clear()
Expand Down Expand Up @@ -421,40 +421,39 @@ def get_renderer(self, cleared=False):
return self.renderer

def tostring_rgb(self):
'''Get the image as an RGB byte string.
"""Get the image as an RGB byte string.

`draw` must be called at least once before this function will work and
to update the renderer for any subsequent changes to the Figure.

Returns
-------
bytes
'''
"""
return self.renderer.tostring_rgb()

def tostring_argb(self):
'''Get the image as an ARGB byte string
"""Get the image as an ARGB byte string.

`draw` must be called at least once before this function will work and
to update the renderer for any subsequent changes to the Figure.

Returns
-------
bytes

'''
"""
return self.renderer.tostring_argb()

def buffer_rgba(self):
'''Get the image as an RGBA byte string.
"""Get the image as a memoryview to the renderer's buffer.

`draw` must be called at least once before this function will work and
to update the renderer for any subsequent changes to the Figure.

Returns
-------
bytes
'''
memoryview
"""
return self.renderer.buffer_rgba()

def print_raw(self, filename_or_obj, *args, **kwargs):
Expand Down