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Add support for metadata= and pil_kwargs= in imsave(). #13902

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Merged
merged 1 commit into from
May 6, 2019
Merged

Add support for metadata= and pil_kwargs= in imsave(). #13902

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4 changes: 4 additions & 0 deletions doc/users/next_whats_new/2019-04-05-AL.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
`~pyplot.imsave` gained support for the ``metadata`` and ``pil_kwargs`` parameters
``````````````````````````````````````````````````````````````````````````````````

These parameters behave similarly as for the `Figure.savefig()` method.
42 changes: 35 additions & 7 deletions lib/matplotlib/image.py
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Expand Up @@ -1431,7 +1431,7 @@ def read_png(*args, **kwargs):


def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
origin=None, dpi=100):
origin=None, dpi=100, *, metadata=None, pil_kwargs=None):
"""
Save an array as an image file.

Expand Down Expand Up @@ -1464,6 +1464,17 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
dpi : int
The DPI to store in the metadata of the file. This does not affect the
resolution of the output image.
metadata : dict, optional
Metadata in the image file. The supported keys depend on the output
format, see the documentation of the respective backends for more
information.
pil_kwargs : dict, optional
If set to a non-None value, always use Pillow to save the figure
(regardless of the output format), and pass these keyword arguments to
`PIL.Image.save`.

If the 'pnginfo' key is present, it completely overrides
*metadata*, including the default 'Software' key.
"""
from matplotlib.figure import Figure
from matplotlib import _png
Expand All @@ -1474,10 +1485,14 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
else rcParams["savefig.format"]).lower()
if format in ["pdf", "ps", "eps", "svg"]:
# Vector formats that are not handled by PIL.
if pil_kwargs is not None:
raise ValueError(
f"Cannot use 'pil_kwargs' when saving to {format}")
fig = Figure(dpi=dpi, frameon=False)
fig.figimage(arr, cmap=cmap, vmin=vmin, vmax=vmax, origin=origin,
resize=True)
fig.savefig(fname, dpi=dpi, format=format, transparent=True)
fig.savefig(fname, dpi=dpi, format=format, transparent=True,
metadata=metadata)
else:
# Don't bother creating an image; this avoids rounding errors on the
# size when dividing and then multiplying by dpi.
Expand All @@ -1488,17 +1503,28 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
if origin == "lower":
arr = arr[::-1]
rgba = sm.to_rgba(arr, bytes=True)
if format == "png":
_png.write_png(rgba, fname, dpi=dpi)
if format == "png" and pil_kwargs is None:
_png.write_png(rgba, fname, dpi=dpi, metadata=metadata)
else:
try:
from PIL import Image
from PIL.PngImagePlugin import PngInfo
except ImportError as exc:
raise ImportError(
f"Saving to {format} requires Pillow") from exc
if pil_kwargs is not None:
raise ImportError("Setting 'pil_kwargs' requires Pillow")
else:
raise ImportError(f"Saving to {format} requires Pillow")
if pil_kwargs is None:
pil_kwargs = {}
pil_shape = (rgba.shape[1], rgba.shape[0])
image = 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 = PngInfo()
for k, v in metadata.items():
pnginfo.add_text(k, v)
pil_kwargs["pnginfo"] = pnginfo
if format in ["jpg", "jpeg"]:
format = "jpeg" # Pillow doesn't recognize "jpg".
color = tuple(
Expand All @@ -1507,7 +1533,9 @@ def imsave(fname, arr, vmin=None, vmax=None, cmap=None, format=None,
background = Image.new("RGB", pil_shape, color)
background.paste(image, image)
image = background
image.save(fname, format=format, dpi=(dpi, dpi))
pil_kwargs.setdefault("format", format)
pil_kwargs.setdefault("dpi", (dpi, dpi))
image.save(fname, **pil_kwargs)


def pil_to_array(pilImage):
Expand Down
23 changes: 23 additions & 0 deletions lib/matplotlib/tests/test_image.py
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Expand Up @@ -213,6 +213,29 @@ def test_imsave_color_alpha():
assert_array_equal(data, arr_buf)


def test_imsave_pil_kwargs_png():
Image = pytest.importorskip("PIL.Image")
from PIL.PngImagePlugin import PngInfo
buf = io.BytesIO()
pnginfo = PngInfo()
pnginfo.add_text("Software", "test")
plt.imsave(buf, [[0, 1], [2, 3]],
format="png", pil_kwargs={"pnginfo": pnginfo})
im = Image.open(buf)
assert im.info["Software"] == "test"


def test_imsave_pil_kwargs_tiff():
Image = pytest.importorskip("PIL.Image")
from PIL.TiffTags import TAGS_V2 as TAGS
buf = io.BytesIO()
pil_kwargs = {"description": "test image"}
plt.imsave(buf, [[0, 1], [2, 3]], format="tiff", pil_kwargs=pil_kwargs)
im = Image.open(buf)
tags = {TAGS[k].name: v for k, v in im.tag_v2.items()}
assert tags["ImageDescription"] == "test image"


@image_comparison(baseline_images=['image_alpha'], remove_text=True)
def test_image_alpha():
plt.figure()
Expand Down