Progressive JPEG is slightly different but JPEG2000 is very interesting. The wavelet transform is pretty clever in how it arranges the frequency components. It

Progressive JPEG is slightly different but JPEG2000 is very interesting. The wavelet transform is pretty clever in how it arranges the frequency components. It's a shame JPEG2000 never took off, probably due to the patent issues. It has a niche in medical imaging though. I wrote my thesis on this topic, over a decade ago now. When doing image recognition you only need to read the first small part of a JPEG2000 file to get good results, which has obvious advantages. You can ignore the high detail bits at the end.