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Document handling of modes when converting to or from NumPy #7049

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Mar 31, 2023
Merged

Document handling of modes when converting to or from NumPy #7049

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e95b55a
Document loss of palette when converting to NumPy
radarhere Mar 31, 2023
485532c
Mention available pixel types when converting from NumPy
radarhere Mar 31, 2023
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18 changes: 13 additions & 5 deletions src/PIL/Image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3031,21 +3031,29 @@ def frombuffer(mode, size, data, decoder_name="raw", *args):
def fromarray(obj, mode=None):
"""
Creates an image memory from an object exporting the array interface
(using the buffer protocol).
(using the buffer protocol)::

from PIL import Image
import numpy as np
a = np.zeros((5, 5))
im = Image.fromarray(a)

If ``obj`` is not contiguous, then the ``tobytes`` method is called
and :py:func:`~PIL.Image.frombuffer` is used.

If you have an image in NumPy::
In the case of NumPy, be aware that Pillow modes do not always correspond
to NumPy dtypes. Pillow modes only offer 1-bit pixels, 8-bit pixels,
32-signed integer pixels and 32-bit floating point pixels.

Pillow images can also be converted to arrays::

from PIL import Image
import numpy as np
im = Image.open("hopper.jpg")
a = np.asarray(im)

Then this can be used to convert it to a Pillow image::

im = Image.fromarray(a)
When converting Pillow images to arrays however, only pixel values are
transferred. This means that P and PA mode images will lose their palette.

:param obj: Object with array interface
:param mode: Optional mode to use when reading ``obj``. Will be determined from
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