Dehydrate and Rehydrate ckpt model

A way to "dehydrate" a dreambooth model down to less than 1GB and "rehydrate" it back to it's original self (same hash). This technically allow to save half the storage space at the cost of requiring rehydration. This could be dynamically implemented in txt2img or img2img given the right hydration code support.

This is how it goes.

Use the ckpt_subtract.py script to subtract the original model from the DB model, leaving behind only the difference between the two.
Compress the resulting model using tar, gzip, etc to roughly 1GB or less
To rehydrate the model simply reverse the process. Add the diff back on top of the original sd15 model (or actually any other models of your choice, can be a different one) with ckpt_add.py.

Requirements

python -m venv venv
.\venv\Scripts\activate
pip install torch
pip install tdqm
pip install numpy

Example

Dehydrate:

python .\ckpt_subtract.py D:\models\sks_man-1e-6-3000-sd15.ckpt D:\models\v1-5-pruned.ckpt --output dehydrated

Dehydrate with no compression:

python .\ckpt_subtract.py D:\models\sks_man-1e-6-3000-sd15.ckpt D:\models\v1-5-pruned.ckpt --output dehydrated --nocompress

Hydrate compressed model:

python .\ckpt_add.py .\dehydrated.pbz2 D:\models\v1-5-pruned.ckpt --output D:\models\sks_man-1e-6-3000-sd15.ckpt

Hydrate uncompressed model:

python .\ckpt_add.py .\dehydrated D:\models\v1-5-pruned.ckpt --output D:\models\sks_man-1e-6-3000-sd15.ckpt

Hydrate with less "presence":

python .\ckpt_add.py .\dehydrated.pbz2 D:\models\v1-5-pruned.ckpt --str -0.01 --output D:\models\sks_man-1e-6-3000-sd15.ckpt

Other tools

There are three extra tools provided:

ckpt_merge.py:

Will merge two models at a specified alpha ratio

ckpt_unmerge.py:

Will unmerge a merged model (A) at a specified alpha ratio by feeding it one of the two original model (B) that was originally merged with (A - B = C). It will extract the residual one. Usefull if you download a merged model but you are missing one of the two that was used to merge. If you have one of them it will give you back the other model in return.

uncompress.py:

Uncompress a dehydrated model. Can greatly speed up rehydration by no requiring the lenghty uncompression phase.