Hi All,
Pillow provides the Python Imaging Library (PIL)
https://pillow.readthedocs.io/en/stable/
and is a standard package in Sage.
Now, in Sage 10.2.rc3, the following code
g = plot(sin(x)) # to generate a png figure
g.save("fig.png") #
from PIL import Image
img = Image.open("fig.png")
img_rgb = img.convert("RGB")
img_rgb.save("fig.jpg")
returns
OSError: encoder jpeg not available
This is actually not surprising since the file
SAGE_ROOT/build/pkgs/pillow/spkg-install.in
contains the line:
PILLOW_CONFIG_SETTINGS="-C debug=true -C jpeg=disable
$PILLOW_CONFIG_SETTINGS"
Is there any reason for "jpeg=disable" ?
Providing PIL without jpeg support seems quite weird...
This issue is not new and was already noticed already 5 years ago:
https://ask.sagemath.org/question/43298
A side effect of this is that the IPyhon rendering of PIL Images via the
rich output mechanism is broken in Sage 10.2.rc3 (but, for some reasons,
not in Sage 10.1):
in a Jupyter notebook, typing
img = Image.open("fig.png")
img
does display the image but after an error message terminating by
ValueError: Could not save to JPEG for display
There is no such error message in Sage 10.1
If we agree to restore jpeg support in Pillow, I have prepared a branch
that does this for Sage 10.2 (simply suppressing the option "jpeg=disable"):
https://github.com/egourgoulhon/sage/tree/pillow_jpeg
and I am happy to submit a PR for this.
Eric.
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