Image optimization is active by default in ifolor Designer. There are two ways to switch image optimization on or off.
When you open your project in ifolor Designer, you can switch image optimization on and off individually for each inserted image by right-clicking --> Image optimization.
If you want to switch off image optimization completely, click on the settings at the top left (cogwheel symbol), then select "Images" in the left-hand column and remove the checkmark from "Activate general image optimization in the lab".