Add wasm jpegls and j2k/htj2k support

[hanayik]

This PR enables WASM builds of dcm2niix that have support for both jpegls and j2k/htj2k using an emscripten build of openjpeg.

An environment manager pixi, has been added to support the WASM build workflow across platforms (macOS/Linux). Note that on macOS-arm64 emscripten must still be installed/managed outside of pixi. Use a tool like homebrew to install it.

Here's the dcm2niix version string, printed to the browser console, where it reports the compiled jpeg support:

Chris Rorden's dcm2niiX version v1.0.20241231  (JP2:OpenJPEG) (JP-LS:CharLS) Clang20.0.0  (32-bit Windows)

The WASM output files with jpeg support are roughly 1.8x the size of the base dcm2niix WASM build (a difference of 397K)

-rwxr-xr-x  1 taylor  staff   879K 19 Jan 21:52 dcm2niix.jpeg.wasm
-rwxr-xr-x  1 taylor  staff   482K 19 Jan 21:52 dcm2niix.wasm

This size increase seems to track well with other browser implementations such as @cornerstonejs/codec-openjpeg which only compiles openjpeg (not combined with something like dcm2niix) and its size is 367 kB

I have also tested the jpeg build of dcm2niix WASM in the browser using the Aliza-DICOM-viewer-HTJ2k/HTJ2K-YBR_ICT.dcm test image that was tested in issue #897. The resulting NIFTI file renders in niivue the same as Slicer3D:

To test this PR locally

You will need:

• NodeJS/NPM
• Emscripten (only needed separately from pixi if on macOS-arm64)
• Pixi
• Make/Cmake

Pixi is used to create the environment for building the WASM port of dcm2niix. To install pixi, follow their instructions.

Note: on macos-arm64, you can get emscripten using homebrew since there is not yet a native arm64 version of emscripten on conda-forge (which is where pixi searches for packages).

Building dcm2niix WASM

# from repo root
pixi run wasm

clean up after build

# from repo root
pixi run clean

[neurolabusc]

Great job.