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Fix pil_to_tensor for 16-bit images - #9640

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Marchematics:contrib/pil-to-tensor-i16
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Fix pil_to_tensor for 16-bit images#9640
Marchematics wants to merge 1 commit into
pytorch:mainfrom
Marchematics:contrib/pil-to-tensor-i16

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Fix pil_to_tensor for 16-bit images.

Copilot AI lite review requested due to automatic review settings August 30, 2026 15:27
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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/vision/9640

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Pull request overview

This PR updates torchvision.transforms.functional.pil_to_tensor to correctly convert 16-bit PIL images into Torch tensors (instead of failing or producing incorrect dtypes), and adds a regression test to validate round-tripping of int16 tensors through ToPILImage + PILToTensor.

Changes:

  • Add explicit PIL mode → NumPy dtype mapping in pil_to_tensor to support 16-bit (I;16) images.
  • Add a unit test that exercises int16 tensor → PIL → tensor conversion.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File Description
torchvision/transforms/functional.py Adds dtype selection logic in pil_to_tensor to handle 16-bit PIL modes.
test/test_transforms.py Adds a regression test ensuring int16 round-trips through PIL conversion.

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Comment on lines +209 to +214
mode_to_nptype = {
"I": np.int32,
"I;16" if sys.byteorder == "little" else "I;16B": np.int16,
"F": np.float32,
}
img = torch.as_tensor(np.array(pic, mode_to_nptype.get(pic.mode, np.uint8), copy=True))
@meta-cla meta-cla Bot added the cla signed label Aug 30, 2026
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Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!

@Marchematics

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Author

Added explicit I;16 and I;16B mappings with regression coverage.

@Marchematics
Marchematics force-pushed the contrib/pil-to-tensor-i16 branch from 159da63 to b7db05b Compare August 30, 2026 19:07
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