Base bitmap functions, for enable the use of the same .
Implements a bitmap with variable bit depth. Use the aliases to initialize them. Note for 16Bit bitmap: It's using the master palette, It's not implementing any 16 bit RGB or RGBA color space directly. Can implement such colorspaces via proper lookup tables. Note for 4Bit bitmap: It's width needs to be an even number (for rendering simplicity), otherwise it'll cause an exception.
Bitmap attributes, mainly for layers.