Another jpeg2000 I'm afraid. I've never had any use for the jpeg2000 datatype for instance.
There was a hefty licensing fee for the software that creates JPEG2000 images. That's why that format never caught on.
Is there a licensing fee for WebP? I don't think so. The only problem with WebP that I've heard about is that it takes longer to compress than a JPEG. Having had the same problem with compressing PNGs on a Classic Amiga, I doubt that will be a huge problem as long as the download speed is accelerated by the improved compression.
