Rendering images from 300 dpi to 72 dpi

[Aurelie Dupont]

Hello,   I have original images with a high resolution of 300 dpi, which I need for printing (PDF). But I do also need the same pictures in about 72 dpi for the presentation on the web.   Does anyone know by which means I can manage rendering a picture from 300dpi to 72dpi in Cocoon?   Thanks for your help, Aur�lie