86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/* ------------------------------------------------------------------------
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System : Manx Aztec C65 Version 3.2b
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MS-DOS cross-development environment
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Platform : Apple IIe 128K PRODOS 8
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Program : d2circ.c
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Description : G2 Library Routine
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Double Hi-Res 140 x 192 x 16 color circle routine
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Using Bresenham Algorithm with crude aspect modification
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in the xterm only. 1 x 2 aspect for a circle.
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for ProDOS 8 Sys Programs
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Uses Page 2 Double Hi-Res to avoid
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ProDOS Sys Program Load Address at 0x2000
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Written by : Bill Buckels
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Date Written : February 2013
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Revision : 1.0 First Release
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Licence : You may use this code for whatever you wish as long
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as you agree that Bill Buckels has no warranty or
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liability obligations whatsoever from said use.
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------------------------------------------------------------------------ */
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d2circle(x1, y1, radius, drawcolor, xmult, xdiv)
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{
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int f = 1 - radius;
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int ddfx = 1;
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int ddfy = -2 * radius;
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int x = 0;
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int y = radius;
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int xxaspect, xyaspect;
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/* top and bottom */
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d2plot(x1, y1 + radius, drawcolor);
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d2plot(x1, y1 - radius, drawcolor);
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/* sides */
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/* a 1 x 2 aspect */
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/* compresses the xterm for a circle */
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if (xmult > 0 && xdiv > xmult) xyaspect = (y * xmult)/xdiv;
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else xyaspect = y;
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d2plot(x1 + xyaspect, y1, drawcolor);
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d2plot(x1 - xyaspect, y1, drawcolor);
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while(x < y)
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{
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if(f >= 0)
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{
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y--;
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ddfy += 2;
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f += ddfy;
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}
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x++;
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ddfx += 2;
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f += ddfx;
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if (xmult > 0 && xdiv > xmult) {
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/* a 1 x 2 aspect */
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/* compresses the xterm for a circle */
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xxaspect = (x * xmult)/xdiv;
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xyaspect = (y * xmult)/xdiv;
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}
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else {
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xxaspect = x;
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xyaspect = y;
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}
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/* top and bottom */
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d2plot(x1 + xxaspect, y1 + y, drawcolor); /* bottom right */
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d2plot(x1 - xxaspect, y1 + y, drawcolor); /* bottom left */
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d2plot(x1 + xxaspect, y1 - y, drawcolor); /* top right */
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d2plot(x1 - xxaspect, y1 - y, drawcolor); /* top left */
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/* sides */
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d2plot(x1 + xyaspect, y1 + x, drawcolor); /* mid bottom right */
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d2plot(x1 - xyaspect, y1 + x, drawcolor); /* mid bottom left */
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d2plot(x1 + xyaspect, y1 - x, drawcolor); /* mid top right */
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d2plot(x1 - xyaspect, y1 - x, drawcolor); /* mid top left */
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}
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return;
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}
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