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circle_lines.c
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131 lines (106 loc) · 3.03 KB
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/* circle_lines --- plot lines but form a circle 2019-04-14 */
/* Copyright (c) 2019 John Honniball, Froods Software Development */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <unistd.h>
#include "hpgllib.h"
void draw_side(const double xc, const double yc, const double radius, const double maxx, const int n);
void draw3lines(const double xc, const double yc, const double x, const double y, const int up, const double maxx);
int main(int argc, char * const argv[])
{
/* Inspired by Sol LeWitt's "Wall Drawing #370",
via a tweet by Paul Ricards. */
int opt;
int side;
int lines;
double height;
double xc, yc;
double maxx, maxy;
double left, right;
double radius;
lines = 64; /* Default for A3 */
while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {
switch (opt) {
case 's':
if (strchr(optarg, '1'))
lines = 128;
else if (strchr(optarg, '2'))
lines = 96;
else if (strchr(optarg, '4'))
lines = 48;
else if (strchr(optarg, '5'))
lines = 32;
case 'n':
case 'o':
case 'p':
case 't':
case 'v':
plotopt(opt, optarg);
break;
default: /* '?' */
fprintf(stderr, "Usage: %s [-p pen] [-s <size>] [-t title]\n", argv[0]);
fprintf(stderr, " <size> ::= A1 | A2 | A3 | A4 | A5\n");
exit(EXIT_FAILURE);
}
}
if (plotbegin(0) < 0) {
fputs("Failed to initialise HPGL library\n", stderr);
exit(EXIT_FAILURE);
}
getplotsize(&maxx, &maxy);
xc = maxx / 2.0;
yc = maxy / 2.0;
height = maxy;
radius = maxy / 2.0;
left = xc - (height / 2.0);
right = xc + (height / 2.0);
/* Draw square border */
rectangle(left, 0.0, right, maxy);
/* Draw central dividing line */
moveto(xc, 0.0);
lineto(xc, maxy);
/* Draw left & right halves of circle */
for (side = 0; side < 2; side++)
draw_side(xc, yc, radius, side ? left : right, lines);
plotend();
return (0);
}
void draw_side(const double xc, const double yc, const double radius, const double maxx, const int n)
{
int up;
int i;
const double delta = (M_PI / 2.0) / (double)n;
double x, y;
up = 0;
for (i = 1; i < n; i++) {
const double theta = i * delta;
x = cos(theta) * radius;
y = sin(theta) * radius;
draw3lines(xc, yc, x, y, up, maxx);
up = !up; /* Draw alternately up & down to save time */
}
}
void draw3lines(const double xc, const double yc, const double x, const double y, const int up, const double maxx)
{
double top, bottom;
if (up) {
top = yc + y;
bottom = yc - y;
}
else {
top = yc - y;
bottom = yc + y;
}
moveto(maxx, top);
if (maxx > xc) {
lineto(xc + x, top);
lineto(xc + x, bottom);
}
else {
lineto(xc - x, top);
lineto(xc - x, bottom);
}
lineto(maxx, bottom);
}