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

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Merged
merged 2 commits into from
Dec 27, 2018
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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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7 changes: 7 additions & 0 deletions doc/api/next_api_changes/2018-07-22-AL.rst
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@@ -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())
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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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25 changes: 12 additions & 13 deletions lib/matplotlib/backends/backend_agg.py
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Expand Up @@ -265,14 +265,14 @@ def points_to_pixels(self, points):
"""
return points * self.dpi / 72

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

def tostring_argb(self):
return self._renderer.tostring_argb()
return np.asarray(self._renderer).take([3, 0, 1, 2], axis=2).tobytes()
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Did you take a look at uses of this and tostring_rgb on things like StackOverflow to confirm that the type change would continue to work as expected in those use-cases?

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Here there is no change to the return type, it was a bytes, it's still a bytes.

There's a change in the return type of buffer_rgba() but that's sort of the whole point of the PR (and it goes back to the old Py2 behavior, and is also clearly better for performance).


def buffer_rgba(self):
return self._renderer.buffer_rgba()
def tostring_rgb(self):
return np.asarray(self._renderer).take([0, 1, 2], axis=2).tobytes()

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):
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23 changes: 0 additions & 23 deletions src/_backend_agg.cpp
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Expand Up @@ -156,29 +156,6 @@ bool RendererAgg::render_clippath(py::PathIterator &clippath,
return has_clippath;
}

void RendererAgg::tostring_rgb(uint8_t *buf)
{
// "Return the rendered buffer as an RGB string"

int row_len = width * 3;

agg::rendering_buffer renderingBufferTmp;
renderingBufferTmp.attach(buf, width, height, row_len);

agg::color_conv(&renderingBufferTmp, &renderingBuffer, agg::color_conv_rgba32_to_rgb24());
}

void RendererAgg::tostring_argb(uint8_t *buf)
{
//"Return the rendered buffer as an RGB string";

int row_len = width * 4;

agg::rendering_buffer renderingBufferTmp;
renderingBufferTmp.attach(buf, width, height, row_len);
agg::color_conv(&renderingBufferTmp, &renderingBuffer, agg::color_conv_rgba32_to_argb32());
}

agg::rect_i RendererAgg::get_content_extents()
{
agg::rect_i r(width, height, 0, 0);
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2 changes: 0 additions & 2 deletions src/_backend_agg.h
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Expand Up @@ -203,8 +203,6 @@ class RendererAgg
ColorArray &colors,
agg::trans_affine &trans);

void tostring_rgb(uint8_t *buf);
void tostring_argb(uint8_t *buf);
agg::rect_i get_content_extents();
void clear();

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34 changes: 0 additions & 34 deletions src/_backend_agg_wrapper.cpp
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Expand Up @@ -525,38 +525,6 @@ PyRendererAgg_draw_gouraud_triangles(PyRendererAgg *self, PyObject *args, PyObje
Py_RETURN_NONE;
}

static PyObject *PyRendererAgg_tostring_rgb(PyRendererAgg *self, PyObject *args, PyObject *kwds)
{
PyObject *buffobj = NULL;

buffobj = PyBytes_FromStringAndSize(NULL, self->x->get_width() * self->x->get_height() * 3);
if (buffobj == NULL) {
return NULL;
}

CALL_CPP_CLEANUP("tostring_rgb",
(self->x->tostring_rgb((uint8_t *)PyBytes_AS_STRING(buffobj))),
Py_DECREF(buffobj));

return buffobj;
}

static PyObject *PyRendererAgg_tostring_argb(PyRendererAgg *self, PyObject *args, PyObject *kwds)
{
PyObject *buffobj = NULL;

buffobj = PyBytes_FromStringAndSize(NULL, self->x->get_width() * self->x->get_height() * 4);
if (buffobj == NULL) {
return NULL;
}

CALL_CPP_CLEANUP("tostring_argb",
(self->x->tostring_argb((uint8_t *)PyBytes_AS_STRING(buffobj))),
Py_DECREF(buffobj));

return buffobj;
}

static PyObject *
PyRendererAgg_get_content_extents(PyRendererAgg *self, PyObject *args, PyObject *kwds)
{
Expand Down Expand Up @@ -664,8 +632,6 @@ static PyTypeObject *PyRendererAgg_init_type(PyObject *m, PyTypeObject *type)
{"draw_gouraud_triangle", (PyCFunction)PyRendererAgg_draw_gouraud_triangle, METH_VARARGS, NULL},
{"draw_gouraud_triangles", (PyCFunction)PyRendererAgg_draw_gouraud_triangles, METH_VARARGS, NULL},

{"tostring_rgb", (PyCFunction)PyRendererAgg_tostring_rgb, METH_NOARGS, NULL},
{"tostring_argb", (PyCFunction)PyRendererAgg_tostring_argb, METH_NOARGS, NULL},
{"get_content_extents", (PyCFunction)PyRendererAgg_get_content_extents, METH_NOARGS, NULL},
{"buffer_rgba", (PyCFunction)PyRendererAgg_buffer_rgba, METH_NOARGS, NULL},
{"clear", (PyCFunction)PyRendererAgg_clear, METH_NOARGS, NULL},
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