[WIP] Adding Stain Normalization Transform for Pathology

[nsrivathsa]

Description

Adds a Transform for CuPy-based Stain Normalization for Pathology.

Status

Work in progress

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[bhashemian]

Well done, @nsrivathsa! I left few comments inline.
In general, can you think of edge cases in physical world for test cases as well, like the situation that we expect to have only one stain so the concentration of the other one is zero.
Also it would be great to have input images that are not uniformly filled.
Keep in mind that writing solid unittests are very important to ensure the correctness of our code and it might take more time than implementing the original functions and classes.

[bhashemian]

@nsrivathsa I see that lines 47-75 for stain extraction are being repeated in line 143-171 for stain normalization. Can you modify the code so that it reuses stain extraction in stain normalization?

[madil90]

/build

[bhashemian]

A variant of this PR is merged.