Ben Sandofsky of Halide has written a deep dive into understanding how the RAW image format works with a focus on Apple’s ProRAW additions and how Halide has adapted to work with it:
ProRAW stores results of computational photography right inside the RAW… Apple worked with Adobe to introduce a new type of tag into the DNG standard, called a “Profile Gain Table Map.” This data gives your editor everything it needs to know to tone map your photo image and end up with results identical to the first party camera. Because it’s separate data, you can turn down its strength, or turn it off completely.
This is a great overview about why something like the RAW format was needed, why photographers use it, and how Apple has cleverly tried to bridge the gap between the principles of RAW and its own in-camera smart processing of images. Even if you never use Halide (which is a really great app, by the way!), this story is worth your attention.