Adds support in augmentation for keypoints

[atuleu]

Short Description

I am interested to use RandAugment for object detection with keypoints. Instead of re-doing everything on my own, I would like to add support for keypoints in the augmentation present in this repo.

Papers

None I know off

Existing Implementations

Already have some PR

Other Information

I would propose to:

• Add BaseImageAugmentationLayer.augment_keypoints(self,keypoints,transformation,**kwargs) method
• Modify BaseImageAugmentationLayer._augment() to augment keypoints if passed as a dict.
• Modify BaseImageAugmentationLayer.get_random_transformation() to accept keypoints as an argument
• Makes sures all augmentations in RandAugment do implement augment_keypoints and augment_bounding_boxes. This will require to re-implement by compositon RandomContrast,RandomBrightness,RandomTranslation

[atuleu]

Leaving this work for a few days leaved me with a few questions.

• I think bounding_box augmentation is erronous for shear and rotation transform. This will lead to larger bounding boxes than the bounding box covering the sheared/rotated object. Shouldn't the library show some kind of warning if approximative bounding boxes augmentation are made ?

• When considering shear/translation/rotation augmentation, if not using a fill_mode=constant or nearest, it could cause small object to be replicated on the image, without a proper bounding box added. _Shouldn't RandomRotation,RandomTranslation,RandomShear layer raise an Error if augment_bounding_boxes or augment_keypoints be called and fill_mode is 'reflect' or 'wrap'_

• When applying bounding boxes / keypoints augmentation, they may fall outside of the image. Should some options be added to clip the boxes afterwards ?

[LukeWood]

Hey @atuleu! Thanks for your enthusiasm and contributions!

Keypoints is definitely in our roadmap, but I want to make sure we get the API right. I'll be sure to spend some time to look over this label type and how other frameworks handle it so we can compare the different approaches.

Are keypoints basically always xy pairs? Are they ever normalized to the image size? These are the questions we need to be sure to answer.

Perhaps @innat, @sayakpaul, or another would know more about the format keypoints tend to come in.

[sayakpaul]

In the past, I have used imgaug for keypoints. In fact, that is what I used in this tutorial: https://keras.io/examples/vision/keypoint_detection/.

You'll notice that the keypoints are normalized w.r.t the spatial resolutions of the input images.

[innat]

@atuleu

I think bounding box augmentation is erroneous for shear and rotation transform. This will lead to larger bounding boxes than the bounding box covering the sheared/rotated object. Shouldn't the library show some kind of warning if approximative bounding boxes augmentation are made ?

Bounding boxes should be clipped in that cases and same goes to keypoint type as well. Isn't it take in account by already in shear transformation? Mentioning @pranavjadhav001 to comment on this as he's working on it now.

[innat]

@LukeWood

I used albumentation for keypoint augmentation and if I remember correctly I didn't have to normalize keypoint to the image size. The keypoint are usually comes in xy pairs. You can go through the following albumentaiton blogs regarding their approaches and API.

• Keypoints augmentation
• Using Albumentations to augment keypoints

[LukeWood]

so maybe we should mirror the bounding box API, but instead of offering a ton of formats only two: xy, rel_xy. Some augmentations (i.e. rotation) will behave a bit differently depending on format, so we cant just assume one.

Thoughts?

[sayakpaul]

Nice one! Reducing the supported formats for this might actually be a better UX.

[atuleu]

@atuleu

I think bounding box augmentation is erroneous for shear and rotation transform. This will lead to larger bounding boxes than the bounding box covering the sheared/rotated object. Shouldn't the library show some kind of warning if approximative bounding boxes augmentation are made ?

Bounding boxes should be clipped in that cases and same goes to keypoint type as well. Isn't it take in account by already in shear transformation? Mentioning @pranavjadhav001 to comment on this as he's working on it now.

@innat

So there was no augment_bounding_box() for RandomShear ( I added it here aa4a178a60bbdccfb9c4881409a652363c51e45b ). There was last week some augment_bounding_box() for RandomRotation , but no clipping.

@LukeWood I think we should go for a reduced amount of format of 'xy' and 'rel_xy'. Then if more format are needed, they could always be added afterwards. Should I go forward and add this to #519 ?

[atuleu]

I won't be able to work on this for a few days, but would happily add keypoints format support to #519 in the end of next week

[atuleu]

So in #519, I Added the following:

• Keypoint format listing ( atm only 'XY' and 'Rel_XY')
• Associated conversion function
• a keypoint_format option to layer affecting image geometry ( RandomRotation, RandomTranslation and RandomShear)
• a clip_points_to_image_size to the above layers, enabled by default that clips/discard bounding boxes / keypoints to the image size
• An example based on the small TFDS AFWL20003D dataset that show how these augmentation works with keypoints.

[atuleu]

Following the discussion in #519, here are the tasks to perform in single PR from atuleu/keras-cv@dev/keypoints:

• [x] create a PR adding support for keypoint formats & utilities (discard out of image, converters, etc) -> #585
• [x] update the BaseImageAugmentationLayer in a PR -> #586
• [ ] add ALL of the no-op augmentations in a single PR; so all of the ones that just return keypoints -> #588
• [ ] Adds a function to generalize how bounding boxes should be augmented -> #599
• [ ] Add augmentation logic to RandomTranslation (with demonstration)
• [ ] Refactor and add augmentation logic to RandomRotation (with demonstration)
• [ ] Imports and add augmentation logic to RandomContrast
• [ ] Imports and add augmentation logic to RandomBrightness
• [ ] Add augmentation logic to RandomResizedCrop
• [ ] Add augmentation logic to RandomShear (with demonstration)

[LukeWood]

Thank you @atuleu for breaking the problem down like this. I appreciate your contributions greatly. Pleasure working together, I'll review these as they come in!

[pranavjadhav001]

@atuleu

I think bounding box augmentation is erroneous for shear and rotation transform. This will lead to larger bounding boxes than the bounding box covering the sheared/rotated object. Shouldn't the library show some kind of warning if approximative bounding boxes augmentation are made ?

Bounding boxes should be clipped in that cases and same goes to keypoint type as well. Isn't it take in account by already in shear transformation? Mentioning @pranavjadhav001 to comment on this as he's working on it now.

For random shear bbox augmentation , we are clipping bboxes to 0- image width/height.

[atuleu]

Request For Comment @LukeWood, @inat, @sayakpaul

I think I am hitting an initial design choice issue at the moment, and I would need some input to help me choose the best options.

The issue comes from the handling of keypoints that may become invalid after an augmentation. My initial thought has suggested by #585 was to simply return in augment_keypoints a ragged tensor of the valid keypoints. It works well with single images, but if you throw in some vectorization, or sequence of transformation (by example in a RandomAugmentationPipeline), well it does not work well. And from reading other issues, RaggedTensor won´t work well with XLA.

Then I would propose again a new design change from what I proposed in #586 :

• keypoints augmentation would accept two keys keypoints and keypoints_mask, the latter will be optional
• Augmentation output will then also be two outputs: a keypoints and a keypoints_mask
• BaseImageAugmentationLayer._format_inputs should create an appropriate keypoints_mask if None is provided, and convert any passed ragged / sparse tensor to dense ones. This is required as if we batch augment, we may have a variable number of keypoints for each batch item, and tf.vectorized_map will for sure not like it. Proper way to deal with it would be to densify inputs at the batch level in that case.
• BaseImageAugmentaionLayer.augment_keypoints() should return modified keypoints and an optional keypoints_mask of valid keypoints. A None value for the mask, would mean no modification of the mask.
• We make sure than in BaseImageAugmenationLayer._augment() the valid keypoint mask is updated by combining passed and potential new masks. This is required, because if we apply two reversing augmentations in a RandomAugmentationPipeline, the second augmentation may bring some keypoints, who became invalid after the first augmentation, back into a valid range. These keypoints should not become valid again ( underlying image data under the keypoint has been most likely destroyed by the augmentation )
• Optional: we make an argument in BaseImageAugmentationLayer() to mask invalid objects, If enabled, in BaseImageAugmentationLayer._format_output() we tf.ragged.boolean_mask() the invalid keypoints and remove the keypoints_mask key of the output. But then it would be done at the batch level and not individual in batch augmentation case, avoiding the vectorization issues.

[divyashreepathihalli]

Hi @atuleu do you have a PR for adding this support?

[atuleu]

Hello,

There was more than a year ago one huge PR to add suport on keypoint. I was asked to make multiple PR, but the very first one, that was held back by the main maintainers. I tried several to update this PR to upstream change but gave up as it seems the repo's maintainer did not want to merge it.

My day to day work is not relying on keras-cv anymore (very much for these reason). I have therefore no incentive to make this PR happen, with the very likeliness it won't get merged again.

Bests,

On Mon, 5 Feb 2024 at 20:12, Divyashree Sreepathihalli < @.***> wrote:

Hi @atuleu https://github.com/atuleu do you have a PR for adding this support?

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[divyashreepathihalli]

@atuleu I am sorry to hear that. I do not have much context on this, but I do think this is valuable. I will leave the issue open to track it.

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