Yes, for '99%' of cameras (bayer pattern ones) half_size is lossless. For most RGB-bayer patterns there is four different pixel positions in 2x2 block, so if you want to recover exact pixel position you need to examine "filter" field which describes exact layout.
There is some 'special cases': CMYG cameras, Leaf cameras with 8x2 blocks, but most cases are simple.
Also, we'll sometimes refactor this place in LibRaw. Having multiple planes will make simpler to deal with multi-planes cameras: Fuji SuperCCD (2 images in one file), Sinar 4-shot and 16-shot.....
Yes, for '99%' of cameras (bayer pattern ones) half_size is lossless. For most RGB-bayer patterns there is four different pixel positions in 2x2 block, so if you want to recover exact pixel position you need to examine "filter" field which describes exact layout.
There is some 'special cases': CMYG cameras, Leaf cameras with 8x2 blocks, but most cases are simple.
Also, we'll sometimes refactor this place in LibRaw. Having multiple planes will make simpler to deal with multi-planes cameras: Fuji SuperCCD (2 images in one file), Sinar 4-shot and 16-shot.....
Sometimes on LibRaw 0.9