DirectDraw enables the creation of multiple palettes that can be attached to off-screen surfaces. When this is done, the off-screen surfaces no longer share the palette of the primary surface. If an off-screen surface with a pixel format different from the primary surface is created, it is assumed that the hardware can use it. For instance, if a paletized off-screen surface is created when the primary surface is in 16-bit color mode, it is assumed that the blitter can convert palettized surfaces to true color during the blit operation.
DirectDraw supports the creation of standard 8-bit palettized surfaces, capable of displaying 256 colors, and two kinds of 4-bit palettized surfaces, each capable of displaying 16 colors. The first kind of 4-bit palettized surface is indexed into a true color palette table; the second kind is indexed into the primary surface indexed palette table. This second type of palette provides 50 percent compression and a layer of indirection to the sprites stored using it.
If these surfaces are to be created, the blitter must be able replace the palette during the blit operation. Therefore, while blitting from one palettized surface to another, the palette is ignored. Palette decoding is only done to true color surfaces, or when the 4-bit palette is an index to an index in the 8-bit palette. In all other cases, the indexed palette is the palette of the destination.
Raster operations for palettized surfaces are ignored. Changing the attached palette of a surface is a very quick operation. All three of these palettized surfaces should be supported as textures on 3D accelerated hardware.