So gzipped base64 can add less than 1% overhead. Of course a binary format can be even more efficient (also when decoding, I imagine) but the question is if the difference is big enough to introduce an entirely new format when base64 data URIs are already widely supported.
Then the other question is why this proposed packed format is better than the dozen already existing formats like Web Archive, CHM, MAFF, MHTML, etc.
You have 2 options.
- Embed images into html (base64, size overhead)
- embed html/css/js into media binaries
.hmml is the packing strategy for option two. 2kb js for encode/decode. And extra rantings around what a 'digital image' is