High CPU usage

When zoomer is running, the CPU for firefox is above 45%. Is there a way to reduced perhaps by changing the configuration?

Smaller images needs less processing. Zoomer is doing constant position and transparency change of images with overlapping. Browsers do not use graphic accelerators so CPU is alone there so there must be CPU usage increase for such operation. When I say size of images that counts both for size in KB and also size of visible area.