Compression by jpeg2000 (nvJPEG2000 library)

Can we do this? It would be very nice for pathology applications. And in particular grayscale

GPU acceleration using the nvJPEG2000 library

Is this something which can be added or is already there

Yes, you just download and install it.
There are examples on:
GitHub - NVIDIA/CUDALibrarySamples: CUDA Library Samples
- Select the nvJPEG2000
- It is a few years old, but looks like it was updated 3 weeks ago