A Pixmap is like a Bitmap. The only difference is that it stores the pixels in reverse order. Where a Bitmap stores the left most pixel in the most significant bits of a word, a Pixmap stores its left most pixel in the least significant bits. That's all.

Why do we need Pixmaps?! They optimize certain drawing routines if it is known that the host OS is itself in Pixmap format. Copy-and-reverse operations of bits (which are supported by FXBlt) are much more expensive than simple copy operations where the bits are already in the same order.