Commodore 128D - Page 123

string, A$, stores a string of zeroes and ones in the computer's mem
ory that make up the picture on the screen. As in all computer graph
ics, the computer has a way it can represent visual graphics with bits
in its memory. Each dot on the screen, called a pixel, has a bit in the
computer's memory that controls it. In standard bit-map mode, if the
bit in memory is equal to a 1 (on), then the pixel on the screen is
turned on. if the controlling bit in memory is equal to a 0 (off), then
the pixel is turned off.
Saving the Picture Data in a Sprite
Your picture is now stored in a string. The next step is to transfer the
picture data from the data string (A$) into the sprite data area so you
can turn it on and animate it. The statement that does this is SPRSAV.
Here are the statements:
SO SPRSAV A$,1:REM STORE DATA STRING IN SPRITE 1
55 SPRSAV A$,2:REM STORE DATA STRING IN SPRITE 2
Your picture data is transferred into sprite 1 and 2. Both sprites have
the same data, so they look exactly the same. You can't see the
sprites yet, because you have to turn them on.
Turning on Sprites
The SPRITE statement turns on a specific sprite (numbered 1
through 8), colors it, specifies its screen priority, expands the sprite's
size and determines the type of sprite display. The screen priority
refers to whether the sprite passes in front of or behind the objects
on the screen. Sprites can be expanded to twice their original size in
either the horizontal or vertical directions. The type of sprite display
determines whether the sprite is a standard bit map sprite* or a mul
ticolor bit mapped sprite. Here are the two statements that turn on
sprites 1 and 2.
60 SPRITE 1,1,7,0,0,0,0:REM TURN QN SPR 1
65 SPRITE 2,1,3,0,0,0,0:REM TURN ON SPR 2
Here's what each of the numbers in the SPRITE statements mean;
SPRITE #,O,C,P,X,Y,M
# —Sprite number (1 through 8)
O—Turn On (0=1) or Off (O = 0)
C —Color (1 through 16)
P — Priority— If P = 0, sprite is in front of objects on the screen
If P = 1, sprite is in back of objects on the screen
115 USING C128 MODE—Color, Animation and Sprite Graphics Statements