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I am working on a mobile web accelerator proxy server that aims to reduce bandwidth usage for mobile clients.

Currently I am looking at image files. The most fail safe way of reducing file size is to use higher compression/lower quality, while maintaining resolution.

However, I think halving the horizontal and vertical resolution of gifs, pngs and jpegs would greatly reduce the bandwidth requirement.

For each of these formats, is it possible to "trick" the browser to render a 500 pixel wide image as if it is having 1000 pixels width?

Remember; I don't control the HTML, JavaScript and CSS.

JPEG has progressive encoding. Could I utilize that? PNG and and GIFs may have a DPI-metadata?

frodeborli
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  • The short answer is no. The HTML defines how an image is treated. If you can't control the HTML, you can't control how the image is rendered when you change the resolution. PNG/JPEG/GIF only contain a single set of size information, not info for actual/rendered. Even DPI information is usually ignored in web browsers and not present in GIFs. JPEG's progressive encoding can get you a smaller file by eliminating the higher AC values, but you'll get the same effect with a lower quality non-progressive JPEG. – BitBank Feb 26 '14 at 18:06
  • I'm thinking about injecting some data-url src for image tags, as sort of a place holder, then inject a script to request the exact resolution dynamically. You should post your comment as an answer if you are sure. I'll accept it, if no other solution arrives. – frodeborli Feb 26 '14 at 18:21

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