Yesterday Apple released to developers the first beta of MacOS 10.13.4, and I was delighted to see that support for encoding HEIF images was included (finally). So naturally, and only a few hours later (sorry for the delay), I've got a pre-release version of Acorn which supports it. My new image processing app also supports HEIF, so if you're in need of converting more than a couple of images to this new format, send me a note.
Now a couple of random thoughts.
The UTI and file extension that Preview.app advertises for HEIF is "public.heic" and .heic. HEIF stands for High Efficiency Image File Format, HEIC stands for… HEIF images encoded with the High Efficiency Video Codec (HEVC). So it's short for HEIHEVC I guess? At any rate, it's getting very confusing on my end as to what to call it, so I'm following Preview's lead and files saved out of Acorn get the file extension of .heic for HEIF images.
Then again, HEIF is a container format. It supports HEVC and H.264. Kind of like QuickTime's .mov format. So maybe .heic makes sense after all, because it's not like we have room for 8 bytes associated with the file to give us any more information such as what app to open it in and the format of the file. Instead, we get an extension and magic headers in the file. But I digress.
HEIF supports up to 16 bits per channel! This is super awesome because it means we've got a great image format that not only compresses images better than JPEG, but we can keep our colors accurate when paired with wide gamut color profiles such as Display P3. Goodbye banding! But there's bad news as well. Apple's encoders both on iOS and MacOS only support 8 bits per channel. So that means if you were wanting to convert your RAW images to HEIF but you wanted to keep your color accuracy, you're out of luck for now.
But it's all a step in the right direction.