Hi @wyli ,

Thanks for your enhancement for ImageDataset.
I think the reason we kept ImageDataset after developed ArrayDataset is that: ImageDataset loads image data and meta_data in this dataset instead of transforms, so it can apply following typical transform chain only for the image data and still return both transformed image data and the meta_data.
For the use case you provided in this PR, it requires every transform in the chain must accept the meta_data arg, then why not use ArrayDataset directly?
And to support mixed transforms that some can accept meta_data and some not, users can refer to this example:
https://github.com/Project-MONAI/MONAI/blob/dev/monai/data/dataset.py#L926
What do you think?

Thanks.

Hi @Nic-Ma, this API is used by multiple tutorials, but it's half baked. here I enhanced it and made a demo to show the usage. Project-MONAI/tutorials#222

Hi @wyli ,

Thanks for your tutorial, may I know why we don't use ArrayDataset for the case in the tutorial? Maybe you can change to show ArrayDataset in the tutorial?
I think we only use ImageDataset in the case that we need the meta_data for the following operations(like saving files) and all the transforms don't need meta_data, otherwise, ArrayDataset may be a better choice.

Thanks.

with this enhancement the imagedataset has better handling of the metadata compared with the arraydataset, now it's a good complimentary to our dataset APIs

Hi @wyli ,

I don't quite understand "ImageDataset has better handling of the metadata compared with the ArrayDataset", could you please help share more details?
I think we discussed to use ArrayDataset and delete ImageDataset, but ImageDataset has 1 benefit that can get both image data and meta_data but only run transform chain on the image data, so we keep it.

Thanks.

the current imagedataset doesn't work with the meta data as reported in #2304, this PR fixes the issue.

OK, I see your point now.
So you mean to support the case that: all the transforms in the Compose chain expect (img, meta) input and ArrayDataset can't support this case if using Compose, right?
That makes sense.

Thanks for your explanation.