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Add cucim.skimage.morphology.medial_axis - #342

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grlee77:add-medial_axis
Aug 3, 2022
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grlee77:add-medial_axis

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@grlee77

@grlee77 grlee77 commented Jul 26, 2022 •

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closes #336

This PR adds a function for skeletonization of 2D images via the medial axis transform.

It should be reviewed after #318 is merged. The new commits only start from 19a6fed.

There is one sequential component to this algorithm that still must be run on the CPU, but the majority of the computations are on the GPU and acceleration is good. I will add benchmark results here soon.

@grlee77 grlee77 added feature request New feature or request non-breaking Introduces a non-breaking change labels Jul 26, 2022
@grlee77 grlee77 added this to the v22.08.00 milestone Jul 26, 2022
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grlee77 requested a review from a team as a code owner July 26, 2022 14:43
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grlee77 commented Jul 27, 2022

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Acceleration is around 10x relative to scikit-image v0.19.3. That is pretty good considering that there is still a sequential portion that needs to run on the GPU.

image.shape = (328, 400)
    Duration (cpu) = 0.0446 +/= 0.0006
    Duration (gpu) = 0.0041 +/= 0.0001
    Acceleration: 11.00
image.shape = (1312, 1600)
    Duration (cpu) = 0.3426 +/= 0.0013
    Duration (gpu) = 0.0284 +/= 0.0003
    Acceleration: 12.07
image.shape = (2624, 3200)
    Duration (cpu) = 1.7736 +/= 0.0006
    Duration (gpu) = 0.1583 +/= 0.0033
    Acceleration: 11.21
image.shape = (5248, 6400)
    Duration (cpu) = 8.8874 +/= 0.0000
    Duration (gpu) = 0.9180 +/= 0.0051
    Acceleration: 9.68

rapids-bot Bot pushed a commit that referenced this pull request Jul 28, 2022
### Overview

closes #319

This PR adds an implementation of `scipy.ndimage.distance_transform_edt`. For each foreground pixel in a binary image, this function computes the minimal Euclidean distance to reach a background pixel. This is a SciPy function rather than a scikit-image one so I have put it under `cucim.core` instead of `cucim.skimage`. Longer term we could move this upstream to CuPy, but I think we want to have a copy here so that we can use it in the near term to implement some of the missing scikit-image functionality. This function is used by the following functions in the scikit-image API, so this PR will help us implement these in future PRs:

`skimage.morphology.medial_axis` (**update**: see #342)
`skimage.segmentation.expand_labels` (**update**: see #341)
`skimage.segmentation.chan_vese` (**update**: see #343)
It is also used in examples related to `skimage.segmentation.watershed` and is needed for implementation of ITK's `SignedMaurerDistanceMapImageFilter` for [itk-cucim](InsightSoftwareConsortium/itk_cucim#13).

The algorithm used here is adapted from the C++ code in the [PBA+ repository](https://github.com/orzzzjq/Parallel-Banding-Algorithm-plus) (MIT-licensed)

### extensions made to PBA+ kernel source
- larger sizes can be supported due to runtime code generation of the integer datatypes and encode/decode functions.

### current known limitations
- 2D and 3D only (this should cover the most common use cases)
- The `sampling` argument is not fully supported. This can likely be done with a bit of effort, but will require modifications to the CUDA kernels
- User-specified output arguments are not currently supported. We can potentially add this in the future
- The indices returned by `return_indices=True` are equally valid, but not always identical to those returned by SciPy. This is because there can be multiple indices with an identical distance, so which one gets chosen in that case is implementation-dependent.

### initial benchmarks relative to SciPy

Here `% true` is the percentage of the image that corresponds to foreground pixels. Even for fairly small images there is some benefit, with the benefit becoming two orders of magnitude at larger sizes.

shape      | % true |  cuCIM |  SciPy  | acceleration
-----------------|--------|---------|---------|--------------
(256, 256) | 5 | 0.00108 | 0.00353 | 3.25
(512, 512) | 5 | 0.00108 | 0.01552 | 14.42
(2048, 2048) | 5 | 0.00252 | 0.34434 | 136.86
(4096, 4096) | 5 | 0.00765 | 1.58948 | 207.88
(32, 32, 32) | 5 | 0.00103 | 0.00305 | 2.98
(128, 128, 128) | 5 | 0.00153 | 0.30103 | 196.26
(256, 256, 256) | 5 | 0.00763 | 3.17872 | 416.37
(384, 384, 384) | 5 | 0.02460 | 14.28779 | 580.89
(256, 256) | 50 | 0.00107 | 0.00430 | 4.01
(512, 512) | 50 | 0.00109 | 0.01878 | 17.30
(2048, 2048) | 50 | 0.00299 | 0.39304 | 131.60
(4096, 4096) | 50 | 0.00896 | 1.84686 | 206.19
(32, 32, 32) | 50 | 0.00102 | 0.00361 | 3.53
(128, 128, 128) | 50 | 0.00163 | 0.31657 | 194.66
(256, 256, 256) | 50 | 0.00914 | 3.35914 | 367.49
(384, 384, 384) | 50 | 0.03005 | 13.83219 | 460.30
(256, 256) | 95 | 0.00107 | 0.00344 | 3.22
(512, 512) | 95 | 0.00108 | 0.01638 | 15.17
(2048, 2048) | 95 | 0.00314 | 0.36996 | 117.81
(4096, 4096) | 95 | 0.00943 | 1.90475 | 202.05
(32, 32, 32) | 95 | 0.00102 | 0.00314 | 3.07
(128, 128, 128) | 95 | 0.00180 | 0.28843 | 159.80
(256, 256, 256) | 95 | 0.01073 | 3.23450 | 301.41
(384, 384, 384) | 95 | 0.03577 | 12.40526 | 346.82

### other comments
- can likely reduce memory overhead and improve performance a bit by refactoring some of the pre/post-processing code into elementwise kernels. (e.g. `encode3d`/`decode3d`, etc.)

- (JK) This may be able to leverage CuPy in the future ( cupy/cupy#6919 )

Authors:
  - Gregory Lee (https://github.com/grlee77)

Approvers:
  - Gigon Bae (https://github.com/gigony)
  - https://github.com/jakirkham

URL: #318
@jakirkham

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@grlee77, can you please take a look at the conflict here? Looks related to PR ( #318 )

@grlee77

grlee77 commented Jul 28, 2022

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fixed the conflict

@jakirkham
jakirkham requested a review from gigony August 1, 2022 23:06
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@gigony, could you please review this as well? 🙂

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Looks good to me!


class TestMedialAxis():
def test_00_00_zeros(self):
'''Test skeletonize on an array of all zeros'''

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nit: just wondering if there is a reason to use ''' instead of """ in this file.

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Yeah we should probably move to """. This is what black does

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Happy to change this to """ and we can probably apply black at some point, but I didn't do it so far for two reasons
1.) It messes with readability of various small test array definitions unless # fmt: off, etc. are placed around them
2.) easier to compare diffs with upstream scikit-image without it.

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Fixed a small conflict above. If that looks ok, please feel free to merge 🙂

@grlee77

grlee77 commented Aug 3, 2022

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@gpucibot merge

@grlee77

grlee77 commented Aug 3, 2022

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@jakirkham: I tried to merge via gpucibot in my previous comment, but it didn't seem to listen to me. Do I need to be granted some permissions here for it to work?

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@gpucibot merge

@rapids-bot
rapids-bot Bot merged commit c834039 into rapidsai:branch-22.08 Aug 3, 2022
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Thanks Ray! 🙏

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[FEA] add cucim.skimage.morphology.medial_axis

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