Skin mode - Laggy UI

I'm a developer myself, I'm curious if you could explain why skin painting was so slow and what you did to fix it?

I've used CxImage library to draw the skins. It was too slow. I've tested the FreeImage library but it is slow too, especially the resizing operation, that very critical for TLB performance. So now I'm using FreeImage for loading skin images and converting them into 32 bpp bitmaps and I wrote own optimized code for resizing and other operations with bitmaps. All these working much faster.