Truecolor pixel formats
In a truecolor video mode the red, green, and blue components for each pixel
are packed directly into the color value, rather than using a palette lookup
table. In a 15-bit mode there are 5 bits for each color, in 16-bit modes
there are 5 bits each of red and blue and six bits of green, and both 24 and
32-bit modes use 8 bits for each color (the 32-bit pixels simply have an
extra padding byte to align the data nicely). The layout of these components
can vary depending on your hardware, but will generally either be RGB or
BGR. Since the layout is not known until you select the video mode you will
be using, you must call set_gfx_mode() before using any of the following
routines!
