Figure 3-8 Combining Bit-Planes - Commodore Amiga Hardware Reference Manual

A Playfield of Three or More Colors
For three or more colors, you need more than one bit-plane. The task here is to define
each bit-plane in such a way that when they are combined for display, each pixel con-
tains the correct combination of bits. This is a little more complicated than a playfield
of one bit-plane. The following examples show a four-color playfield, but the basic idea
and procedures are the same for playfields containing up to 32 colors.
Figure 3-8 shows two bit-planes forming a four-color playfield:
Image in
Bit-Plane 2
OOO~OOOO
000 0 0 0 0 0
o
0 0 0 0 0 0 0
11100111
11100111
000[J]1000
000 1 1 000
000 1 100 0
Image in
Bit-Plane
o
0 0[TI1 000
000 1 100 0
000 1 100 0
11100111
11100111
o
0 0[J]1 0 0 0
000 1 1 000
000 1 1 000
~/
Results in a display
similar to this:
Figure 3-8: Combining Bit-planes
Color 00
(background)
You place the correct Is and Os in both bit-planes to give each pixel in the picture above
the correct color.
In a single play field you can combine up to five bit-planes in this way. Using five bit-
planes allows a choice of 32 different colors for any single pixel. The play field color selec-
tion charts at the end of this chapter summarize the bit combinations for playfields
made from four and five bit-planes.
Play field Hardware 45