Fast Drawing of Non-32bpp Images with System.Drawing
It is a well-known fact that when drawing images to the screen that are a different pixel format than the screen's pixel format, format conversion must be performed. GDI+ provides the CachedBitmap class to facilitate easy caching of a converted version of a bitmap. However, this functionality is not exposed in .NET, so normally bitmaps that do not match the screen format are converted on each drawing call.