FLIF: Free Lossless Image Format
nickweller sends a link to an informational post about FLIF, the Free, Lossless Image Format. It claims to outperform PNG, lossless WebP, and other popular formats on any kind of image. "On photographs, PNG performs poorly while WebP, BPG and JPEG 2000 compress well (see plot on the left). On medical images, PNG and WebP perform relatively poorly while BPG and JPEG 2000 work well (see middle plot). On geographical maps, BPG and JPEG 2000 perform (extremely) poorly while while PNG and WebP work well (see plot on the right). In each of these three examples, FLIF performs well — even better than any of the others." FLIF uses progressive decoding to provide fully-formed lossy images from partial downloads in bandwidth-constrained situations. Best of all, FLIF is free software, released under the GNU GPLv3.
How much CPU time does it take to compress vs the others?
How much memory does it need to compress vs the others?
How much CPU and memory does it take to decompress vs the others?
Hard to say it's better without a complete picture.
You're out of touch with half of the world. Bandwidth is extremely expensive and unreliable. The most popular browser in India simply doesn't load images, unless you explicitly click on them. Efficient progressive image formats would be great in those markets.
And if you told Google you could use half or less of the storage space for all images all of a sudden of course they would take you up on it. Storage is cheap, but definitely not free.