A.P.P.L.E. member Dr. Marc A. Golombeck has developed a Double Low Resolution graphics amper-library for the Apple IIe Enhanced, IIc, and the IIgs. This library allows users to perform many advanced graphics functions in Double Lo-Res mode (80 x 48 pixels in 16 color mode) with simple to use amper routines all based in Applesoft BASIC.
The Double Low-Resolution Amper Library includes a host of routines including:
- &GR: switches to double LORES mode and clears the screen
- &TEXT: returns to 40-column text mode
- &COLOR=: sets the plotting color (range: 0..15)
- &PLOT X,Y[,COLOR]:plots a pixel at X,Y. The parameter COLOR is optional.
- &SCRN(X,Y,C%): reads out MAIN or AUX memory depending on the given coordinates and returns the color value C% of the selected pixel (range: $00..$0F / 0..15)
- &VLIN Y1,Y2,X[,COLOR]: plots a vertical line from Y1 to Y2 at column X. The parameter COLOR is optional.
- &HLIN X1,X2,Y[,COLOR]: plots a horizontal line from X1 to X2 at row Y. The parameter COLOR is optional.
With these routines, you can write Applesoft programs like the following program which prints a kaleidoscope of colors to the display screen:
10 REM DOLORES KALEIDOSCOPE
15 REM LOAD DLCOREAMP FIRST!
20 E = - 16384
30 & GR
40 FOR W = 3 TO 50:
W1 = W / 73:
FOR I = 1 TO 19:
W2 = I * W1:
I1 = 3 / (I + 3):
FOR J = 0 TO 19:
K = I + J
45 IF PEEK (E) > 128 THEN
300
50 C = J * I1 + W2
60 & PLOT 20 + I,3 + K,C:
& PLOT 20 + K,3 + I,C:
& PLOT 60 - I,43 - K,C:
& PLOT 60 - K,43 - I,C
70 & PLOT 20 + K,43 - I,C:
& PLOT 60 - I,3 + K,C:
& PLOT 20 + I,43 - K,C:
& PLOT 60 - K,3 + I,C
80 NEXT J,I,W
90 GOTO 40: REM RESTART
300 & TEXT : ENDThe resulting image on the Apple II display screen with the library loaded and the program run will look something like this:
For more information about the Double Low-Res Amper Library, Check out Marc’s website at: http://www.golombeck.eu/index.php?id=48&L=1
