[jpap]

While the full standard text and machinery can get quite complex, you can still construct relatively simple files housing a single image, thumbnail, and Exif that isn't that much more complex than a typical JPEG file. Compared to JPEG, where you need to define quantization tables, Huffman tables, etc. in marker segments, much of the codec-related complexity in HEIF is layered within the compressed image payload (e.g. HEVC NAL units).

Besides the coding efficiency, JPEG really hit the big time because of the readily available libjpeg cross-platform implementation. In this case, HEIF can leverage existing implementations of the ISO Base Media File Format box model; it builds heavily on that standard.

Nokia is doing the right thing by releasing their format handling library, though perhaps they could loosen up their license to include commercial use. ;-) Hopefully there are some developers amongst us inspired enough to start a new open project that, like libjpeg, brings HEIF to the masses.