Responsive image with different ratio

Hi,

I’ve found a lot of plugins to manage responsive images. But then don’t comply exactly with my current need. Which is:

I would like to load 2 different pictures with different size ratio depending on the device.

For example, my content picture should be:
– 1280x768px when on desktop
– but only 768x768px when browsing via a mobile.

I could not find any plugin which would let me update a second “mobile-friendly” picture with every assets.

Thanks for your help.

Yann