I wanted a reasonably sized photographic image with a 24-bit alpha channel. So I used a JPEG for what JPEGs are good for and a PNG for what PNGs are good for… I combined them using an HTML5 canvas element and then inserted into the DOM. The results look the same as using a normal 24-bit PNG but are one-half to one-sixth the size. In one case we got a 573KB 24-bit PNG down to a 49KB JPEG with a 4KB