Texture Format Selection Rules
When you use a device-independent source image to create a device-dependent texture surface for rendering, the rules are (in order of precedence):
1. Preserve RGB/palettized nature
2. Preserve alpha channel
3. Preserve bit depth or palette size
4. Preserve RBGA masks
5. Prefer 8-bit palettized or 16-bit RGB
For more information about texture pixel formats, see Texture Map Formats.
For related information, see IDirect3DRMTexture and IDirect3DRMTexture2.