Module or code to show different resolution of a picture in mobile version

[zsadam]

Hello mates,

I tried to find without success a module (best free) or a script/code which would solve this issue: I want that for example picture in my custom text blocks module would show lets say: pictureDESKTOP.jpg but if someone would watch it on mobile it would show pictureMOBILE.jpg where pictureMOBILE.jpg would be the same picture as pictureDESKTOP.jp just smaller resolution for faster loading and saving data.

Thanks in advance for any advice!