RAW Image file - what format is my data in?

The name RAW comes from the fact that the values stored in the file are not pixel RGB values, but the raw values that were measured from the camera itself. The values have meaning only if you know how the camera works. There are some standards, but really, you should just consider RAW to be a collection of poorly defined, undocumented, proprietary formats that probably won't intuitively match any idea you have about how images are stored.

Check out DCRaw -- it's the code that nearly every program that supports RAW uses

https://www.dechifro.org/dcraw/

The author reverse-engineered and implemented nearly every proprietary RAW format -- and keeps it up to date.

The other answers are correct, RAW is not a standard, it's shorthand. Camera CCDs often do not have separate red, green and blue pixels for each pixel, instead, they will use what's called a Bayer Pattern and then only save the pixel values for that pattern. Then, you will need to convert that pattern to rgb values.

Also, for the bonus question, if you are simply trying to convert a RGB image to grayscale, or something like that, you can either use the matrix operators, or call convertTO