New drawing: truchet1, the first Truchet tile plot. This plot draws a…

… 12x12 grid of Truchet tiles using arcs. Might be slow to draw on some plotters.

.gitignore

@@ -59,5 +59,6 @@ superellipse
 sutpent
 ternary_arcs
 tree
+truchet1
 twist
 zigzag

Makefile

@@ -23,7 +23,7 @@ HPGL=flake.hpgl op.hpgl dala1.hpgl hconic2.hpgl tree.hpgl dome.hpgl \
      morphpoly.hpgl pin_circle.hpgl isogrid.hpgl circle_lines.hpgl \
      star_grid.hpgl ternary_arcs.hpgl hexspiral.hpgl poly_oval.hpgl \
      libtest.hpgl linetiles.hpgl a6cardlabels.hpgl octoflower.hpgl \
-     circle4.hpgl
+     circle4.hpgl truchet1.hpgl
 
 SVG=$(HPGL:.hpgl=.svg)
 
@@ -148,6 +148,15 @@ ternary_arcs: ternary_arcs.o hpgllib.o
 ternary_arcs.o: ternary_arcs.c hpgllib.h
 	$(CC) $(CFLAGS) -o $@ ternary_arcs.c
 
+truchet1.hpgl: truchet1 Makefile
+	./truchet1 $(TITLE) $(BOLDPEN) -o $@
+
+truchet1: truchet1.o hpgllib.o
+	$(LD) -o $@ truchet1.o hpgllib.o -lm
+
+truchet1.o: truchet1.c hpgllib.h
+	$(CC) $(CFLAGS) -o $@ truchet1.c
+
 poly_oval.hpgl: poly_oval Makefile
 	./poly_oval $(TITLE) $(BOLDPEN) -o $@
 

truchet1.c

@@ -0,0 +1,147 @@
+/* truchet1 --- draw Truchet tiles with arcs on them        2020-08-26 */
+/* Copyright (c) 2020 John Honniball, Froods Software Development      */
+
+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <time.h>
+#include "hpgllib.h"
+
+
+void drawtile(const double x, const double y, const double wd, const double ht, const int tile_type);
+
+
+int main(int argc, char * const argv[])
+{
+   /* Inspired by a tweet on #plottertwitter */
+   int opt;
+   int i, j;
+   int ngridx = 12;
+   int ngridy = 12;
+   int tile_type;
+   double x, y;
+   double xc;
+   double maxx, maxy;
+   double height;
+   double gridw, gridh;
+   double gridx0;
+
+   while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {
+      switch (opt) {
+      case 's':
+         if (strchr(optarg, '1')) {
+            ngridx = ngridy = 32;
+         }
+         else if (strchr(optarg, '2')) {
+            ngridx = ngridy = 14; // If A1 is 32, A2 should be 22, but that's too slow
+         }
+
+      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);
+      }
+   }
+
+   srand((unsigned int)time(NULL));
+
+   if (plotbegin(0) < 0) {
+      fputs("Failed to initialise HPGL library\n", stderr);
+      exit(EXIT_FAILURE);
+   }
+
+   getplotsize(&maxx, &maxy);
+
+   xc = maxx / 2.0;
+
+   height = maxy;
+
+   gridx0 = xc - (height / 2.0);
+
+   gridw = maxy / ngridx;
+   gridh = maxy / ngridy;
+
+   const double bigr = gridw / sqrt(2.0);
+   const double smallr = gridw - bigr;
+
+   for (i = 0; i < ngridx; i++) {
+      x = gridx0 + (i * gridw);
+
+      moveto(x + smallr, maxy);
+      lineto(x + bigr, maxy);
+   }
+
+   for (i = 0; i < ngridy; i++) {
+      y = i * gridh;
+
+      moveto(gridx0, y + smallr);
+      lineto(gridx0, y + bigr);
+   }
+
+   for (i = 0; i < ngridx; i++) {
+      x = gridx0 + (i * gridw);
+
+      moveto(x + smallr, 0.0);
+      lineto(x + bigr, 0.0);
+   }
+
+   for (i = 0; i < ngridy; i++) {
+      y = i * gridh;
+
+      moveto(gridx0 + maxy, y + smallr);
+      lineto(gridx0 + maxy, y + bigr);
+   }
+
+   for (i = 0; i < ngridy; i++) {
+      for (j = 0; j < ngridx; j++) {
+         x = gridx0 + (j * gridw);
+         y = i * gridh;
+//       tile_type = (i + j) % 2;
+         tile_type = rand() / (RAND_MAX / 2);
+         drawtile(x, y, gridw, gridh, tile_type);
+      }
+   }
+
+   plotend();
+
+   return (0);
+}
+
+
+void drawtile(const double x, const double y, const double wd, const double ht, const int tile_type)
+{
+   const double bigr = wd / sqrt(2.0);
+   const double smallr = wd - bigr;
+
+   switch (tile_type) {
+   case 0:
+      moveto(x + wd, y + smallr);
+      arc(x + wd, y, 90.0);
+      moveto(x + smallr, y);
+      arc(x + wd, y, -90.0);
+      moveto(x + bigr, y + ht);
+      arc(x, y + ht, -90.0);
+      moveto(x, y + bigr);
+      arc(x, y + ht, 90.0);
+      break;
+   case 1:
+      moveto(x, y + smallr);
+      arc(x, y, -90.0);
+      moveto(x + bigr, y);
+      arc(x, y, 90.0);
+      moveto(x + smallr, y + ht);
+      arc(x + wd, y + ht, 90.0);
+      moveto(x + wd, y + bigr);
+      arc(x + wd, y + ht, -90.0);
+      break;
+   }
+}