Add support for flow batches in flow_to_image

[NicolasHug]

Follow up to #5134 and to #5091, this PR adds support for batches of flows to the flow_to_image() util.

CC @oke-aditya

[facebook-github-bot]

💊 CI failures summary and remediations

As of commit a1add53 (more details on the Dr. CI page):

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• 2/2 failures introduced in this PR

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🕵️ 1 new failure recognized by patterns

The following CI failures do not appear to be due to upstream breakages:

unittest_linux_gpu_py3.8 (1/1)

Step: "Run tests" (full log | diagnosis details | 🔁 rerun)

test/test_utils.py::test_flow_to_image_errors[i...type torch.float] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_utils.py::test_draw_keypoints_colored[red] �[33mSKIPPED�[0m (We're ...)�[31m [ 99%]�[0m

test/test_utils.py::test_draw_keypoints_colored[#FF00FF] �[33mSKIPPED�[0m (We...)�[31m [ 99%]�[0m

test/test_utils.py::test_draw_keypoints_colored[colors2] �[33mSKIPPED�[0m (We...)�[31m [ 99%]�[0m

test/test_utils.py::test_draw_keypoints_errors �[33mSKIPPED�[0m (We're in a C...)�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image[True] �[33mSKIPPED�[0m (We're in a Cir...)�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image[False] �[33mSKIPPED�[0m (We're in a Ci...)�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image_errors[input_flow0-Input flow should have shape] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image_errors[input_flow1-Input flow should have shape] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image_errors[input_flow2-Input flow should have shape] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image_errors[input_flow3-Input flow should have shape] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_utils.py::test_flow_to_image_errors[input_flow4-Flow should be of dtype torch.float] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_frame_reading �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/v_SoccerJuggling_g23_c01.avi-8.0-True] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/v_SoccerJuggling_g23_c01.avi-8.0-False] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/v_SoccerJuggling_g24_c01.avi-8.0-True] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/v_SoccerJuggling_g24_c01.avi-8.0-False] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/R6llTwEh07w.mp4-10.0-True] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/R6llTwEh07w.mp4-10.0-False] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/SOX5yA1l24A.mp4-11.0-True] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/SOX5yA1l24A.mp4-11.0-False] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

test/test_video_gpu_decoder.py::TestVideoGPUDecoder::test_seek_reading[/home/circleci/project/test/assets/videos/WUzgd7C1pWA.mp4-11.0-True] �[33mSKIPPED�[0m�[31m [ 99%]�[0m

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1 failure not recognized by patterns:

Job	Step	Action
cmake_macos_cpu	curl -o conda.sh https://repo.anaconda.com/miniconda/Miniconda3-latest-MacOSX-x86_64.sh
sh conda.sh -b
source $HOME/miniconda3/bin/activate
conda install -yq conda-build cmake
packaging/build_cmake.sh
	🔁 rerun

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[datumbox]

LGTM, thanks!

[oke-aditya]

One small doubt.

Does this modify flow inplace?

[NicolasHug]

No, the 2 objects may be a view on the same underlying memory, but they're different objects

In [1]: import torch
torch.tensor
In [2]: a = torch.tensor([1, 2])

In [3]: b = a[None]

In [4]: b is a
Out[4]: False

In [5]: a, b
Out[5]: (tensor([1, 2]), tensor([[1, 2]]))

[oke-aditya]

Thanks for clarification. Will note this.