1 files changed, 30 insertions, 0 deletions
diff --git a/src/cmd/map/libmap/trapezoidal.c b/src/cmd/map/libmap/trapezoidal.c
new file mode 100644
index 00000000..977cf60c
--- /dev/null
+++ b/src/cmd/map/libmap/trapezoidal.c
@@ -0,0 +1,30 @@
+#include <u.h>
+#include <libc.h>
+#include "map.h"
+
+static struct coord stdpar0, stdpar1;
+static double k;
+static double yeq;
+
+static int
+Xtrapezoidal(struct place *place, double *x, double *y)
+{
+	*y = yeq + place->nlat.l;
+	*x = *y*k*place->wlon.l;
+	return 1;
+}
+
+proj
+trapezoidal(double par0, double par1)
+{
+	if(fabs(fabs(par0)-fabs(par1))<.1)
+		return rectangular(par0);
+	deg2rad(par0,&stdpar0);
+	deg2rad(par1,&stdpar1);
+	if(fabs(par1-par0) < .1)
+		k = stdpar1.s;
+	else
+		k = (stdpar1.c-stdpar0.c)/(stdpar0.l-stdpar1.l);
+	yeq = -stdpar1.l - stdpar1.c/k;
+	return Xtrapezoidal;
+}