Adding your own custom transforms

[vikashg]

Hello Team,
I was wondering if there is resource guide to adding custom transforms ?
If we need to add new transforms should we be looking at the existing transforms and creating a new one and adding the appropriate hooks at different places ? or is there any better method to do that.

Thanks
Vikash

[Nic-Ma]

Hi @vikashg ,

Please check the "How do I create a custom transform?" part in this tutorial:
https://github.com/Project-MONAI/MONAIBootcamp2021/blob/main/day1/1.%20Getting%20Started%20with%20MONAI.ipynb

Thanks.

[vikashg]

Here is the gist I have tried to give as much information in the code. But please let me know if more information is needed.

[ericspod]

How is this transform used? If your data to be passed into a Dataset object is a list of filenames then this transform will be given one filename at a time rather than whole lists, so your initial data should list of lists of filenames. In your example code:

transform = Compose([LoadImageList()])
img_array = transform(listOfImages)

Compose will break the list of images into individual entries and passed those to the transform sequence then recollate the results together. Something like this should work:

transform = Compose([LoadImageList()])
img_array = transform([listOfImages])  # single item dataset

[vikashg]

The training data will be list of list of images... I see what you did there. Yes If I call the transform as you mentioned it works. I feel stupid :)
Thanks @ericspod. While we are on the topic, as you can see I am kind of copy-pasting bunch of code from the LoadImage transform. I was wondering if you have a better solution.

[ericspod]

You could inherit from LoadImage directly and override the methods you want to change. I think your constructor and that for LoadImage are the same so that should work.

[vikashg]

Ya I could do that. For some reason, I didnt want to inherit from LoadImage. Thanks a ton. It solves a lot of problems I was struggling with for 2 days.