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Fix image plotting in Cairo backends #6602

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Merged
tacaswell merged 2 commits into from
Jun 20, 2016
Merged

Fix image plotting in Cairo backends #6602

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80052ff
WIP solution to #6562
jenshnielsen Jun 18, 2016
5aa9b50
Correct indent
jenshnielsen Jun 20, 2016
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37 changes: 34 additions & 3 deletions lib/matplotlib/backends/backend_cairo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,21 @@ def _fn_name(): return sys._getframe(1).f_code.co_name
BYTE_FORMAT = 1 # ARGB


class ArrayWrapper:
"""Thin wrapper around numpy ndarray to expose the interface
expected by cairocffi. Basically replicates the
array.array interface.
"""
def __init__(self, myarray):
self.__array = myarray
self.__data = myarray.ctypes.data
self.__size = len(myarray.flatten())
self.itemsize = myarray.itemsize

def buffer_info(self):
return (self.__data, self.__size)


class RendererCairo(RendererBase):
fontweights = {
100 : cairo.FONT_WEIGHT_NORMAL,
Expand Down Expand Up @@ -175,9 +190,25 @@ def draw_image(self, gc, x, y, im):
im = im[:, :, (2, 1, 0, 3)]
else:
im = im[:, :, (3, 0, 1, 2)]
surface = cairo.ImageSurface.create_for_data(
memoryview(im.flatten()), cairo.FORMAT_ARGB32, im.shape[1], im.shape[0],
im.shape[1]*4)
if HAS_CAIRO_CFFI:
# cairocffi tries to use the buffer_info from array.array
# that we replicate in ArrayWrapper and alternatively falls back
# on ctypes to get a pointer to the numpy array. This works
# correctly on a numpy array in python3 but not 2.7. We replicate
# the array.array functionality here to get cross version support.
imbuffer = ArrayWrapper(im.flatten())
else:
# py2cairo uses PyObject_AsWriteBuffer
# to get a pointer to the numpy array this works correctly
# on a regular numpy array but not on a memory view.
# At the time of writing the latest release version of
# py3cairo still does not support create_for_data
imbuffer = im.flatten()
surface = cairo.ImageSurface.create_for_data(imbuffer,
cairo.FORMAT_ARGB32,
im.shape[1],
im.shape[0],
im.shape[1]*4)
ctx = gc.ctx
y = self.height - y - im.shape[0]

Expand Down