Commodore Plus 4 - Page 206

194 Programming Graphics
have changed the foreground color since drawing in that cell, the foreground
colored pixels will change color, even though you are drawing in background
color.
High-Resolution Colors Example Program
This example program illustrates the color limitations of high-resolution
graphics mode. Note that the coordinates of the boxes in the first series are
incremented by 10. The character boundaries are therefore frequently crossed
and a "bleeding" of colors is observed. The coordinates of the boxes in the second
series are incremented by eight (and start on a character boundary). Therefore, no
character boundaries are crossed and the colors remain true.
10 GRAPHIC1,1
SO FORX=0TO190STEP10
30 COLOR1,((X/1O)AND15)+1,5
40 B0X,X,X,X+16,X+10,,l
50 NEXT
60 F0RX=0T0192STEP8
70 COLOR1,((X/8)AND15)+1,5
80 B0X,X+64,X,X+80,X+8,,l
90 NEXT
100 COLOR1AACHAR,5,20/'HITKEY''
110 GETKEYK$:GRAPHIC0
Line-by-Line Explanation
10 Enter high-resolution graphics mode (and clear graphics screen).
20 First series of box coordinates are incremented by 10.
30 Choose a new foreground color for each box.
40 Draw a box 16 by 10 at the current coordinates with foreground color
and fill it in.
50 Get the next set of coordinates.
60 Second series of box coordinates are incremented by 8.
70 Choose a new foreground color for each box.
80 Draw a box 16 by 8 at the current coordinates with foreground color and
fill it in.
90 Get the next set of coordinates.
100 Change foreground color to black and plot "HIT KEY".
110 Wait for a key, then return to text mode.