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Reuse png metadata handling of imsave() in FigureCanvasAgg.print_png(). #15435

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Merged
merged 4 commits into from
May 29, 2020
Merged

Reuse png metadata handling of imsave() in FigureCanvasAgg.print_png(). #15435

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7aad47a
Reuse png metadata handling of imsave() in FigureCanvasAgg.print_png().
anntzer Oct 17, 2019
c212f2f
Warn when pil_kwargs["pnginfo"] overrides metadata.
anntzer Oct 18, 2019
83f82f2
Save a couple of numpy conversions.
anntzer May 23, 2020
92a33aa
Skip None entries in png metadata.
anntzer May 29, 2020
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28 changes: 5 additions & 23 deletions lib/matplotlib/backends/backend_agg.py
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,6 @@

import numpy as np
from PIL import Image
from PIL.PngImagePlugin import PngInfo

import matplotlib as mpl
from matplotlib import cbook
Expand Down Expand Up @@ -485,8 +484,8 @@ def print_png(self, filename_or_obj, *args,

Other keywords may be invented for other purposes.

If 'Software' is not given, an autogenerated value for matplotlib
will be used.
If 'Software' is not given, an autogenerated value for Matplotlib
will be used. This can be removed by setting it to *None*.

For more details see the `PNG specification`_.

Expand All @@ -499,27 +498,10 @@ def print_png(self, filename_or_obj, *args,
If the 'pnginfo' key is present, it completely overrides
*metadata*, including the default 'Software' key.
"""

if metadata is None:
metadata = {}
if pil_kwargs is None:
pil_kwargs = {}
metadata = {
"Software":
f"matplotlib version{mpl.__version__}, http://matplotlib.org/",
**metadata,
}
FigureCanvasAgg.draw(self)
# Only use the metadata kwarg if pnginfo is not set, because the
# semantics of duplicate keys in pnginfo is unclear.
if "pnginfo" not in pil_kwargs:
pnginfo = PngInfo()
for k, v in metadata.items():
pnginfo.add_text(k, v)
pil_kwargs["pnginfo"] = pnginfo
pil_kwargs.setdefault("dpi", (self.figure.dpi, self.figure.dpi))
(Image.fromarray(np.asarray(self.buffer_rgba()))
.save(filename_or_obj, format="png", **pil_kwargs))
mpl.image.imsave(
filename_or_obj, self.buffer_rgba(), format="png", origin="upper",
dpi=self.figure.dpi, metadata=metadata, pil_kwargs=pil_kwargs)

def print_to_buffer(self):
FigureCanvasAgg.draw(self)
Expand Down
33 changes: 26 additions & 7 deletions lib/matplotlib/image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1514,18 +1514,37 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
origin = mpl.rcParams["image.origin"]
if origin == "lower":
arr = arr[::-1]
rgba = sm.to_rgba(arr, bytes=True)
if (isinstance(arr, memoryview) and arr.format == "B"
and arr.ndim == 3 and arr.shape[-1] == 4):
# Such an ``arr`` would also be handled fine by sm.to_rgba (after
# casting with asarray), but it is useful to special-case it
# because that's what backend_agg passes, and can be in fact used
# as is, saving a few operations.
rgba = arr
else:
rgba = sm.to_rgba(arr, bytes=True)
if pil_kwargs is None:
pil_kwargs = {}
pil_shape = (rgba.shape[1], rgba.shape[0])
image = PIL.Image.frombuffer(
"RGBA", pil_shape, rgba, "raw", "RGBA", 0, 1)
if format == "png" and metadata is not None:
# cf. backend_agg's print_png.
pnginfo = PIL.PngImagePlugin.PngInfo()
for k, v in metadata.items():
pnginfo.add_text(k, v)
pil_kwargs["pnginfo"] = pnginfo
if format == "png":
# Only use the metadata kwarg if pnginfo is not set, because the
# semantics of duplicate keys in pnginfo is unclear.
if "pnginfo" in pil_kwargs:
if metadata:
cbook._warn_external("'metadata' is overridden by the "
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I could also see a case for raising, but warning seems like a step in the right direction.

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I left this as is but can raise too, just pick one.

"'pnginfo' entry in 'pil_kwargs'.")
else:
metadata = {
"Software": (f"Matplotlib version{mpl.__version__}, "
f"https://matplotlib.org/"),
**(metadata if metadata is not None else {}),
}
pil_kwargs["pnginfo"] = pnginfo = PIL.PngImagePlugin.PngInfo()
for k, v in metadata.items():
if v is not None:
pnginfo.add_text(k, v)
if format in ["jpg", "jpeg"]:
format = "jpeg" # Pillow doesn't recognize "jpg".
facecolor = mpl.rcParams["savefig.facecolor"]
Expand Down