1 files changed, 85 insertions, 0 deletions
diff --git a/rframes.c b/rframes.c
new file mode 100644
index 0000000..cfb1158
--- /dev/null
+++ b/rframes.c
@@ -0,0 +1,85 @@
+#include <u.h>
+#include <libc.h>
+#include <geometry.h>
+
+void
+printm(Matrix m)
+{
+	int i, j;
+
+	for(i = 0; i < 3; i++){
+		for(j = 0; j < 3; j++)
+			print("\t%g", m[i][j]);
+		print("\n");
+	}
+}
+
+Point2
+rfxform(Point2 p, RFrame rf)
+{
+	Matrix m = {
+		rf.bx.x, rf.by.x, 0,
+		rf.bx.y, rf.by.y, 0,
+		0, 0, 1
+	};
+	invm(m);
+//	printm(m);
+	return xform(subpt2(p, rf.p), m);
+}
+
+Point2
+invrfxform(Point2 p, RFrame rf)
+{
+	Matrix m = {
+		rf.bx.x, rf.by.x, 0,
+		rf.bx.y, rf.by.y, 0,
+		0, 0, 1
+	};
+//	printm(m);
+	return addpt2(xform(p, m), rf.p);
+}
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s srcp srcbx srcby dstp dstbx dstby p\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char *argv[])
+{
+	char *s;
+	RFrame src, dst;
+	Point2 p;
+
+	GEOMfmtinstall();
+	ARGBEGIN{
+	default: usage();
+	}ARGEND;
+	if(argc != 7)
+		usage();
+
+	s = argv[0]; src.p.x = strtod(s, &s); src.p.y = strtod(s, &s); src.p.w = strtod(s, &s);
+	s = argv[1]; src.bx.x = strtod(s, &s); src.bx.y = strtod(s, &s); src.bx.w = 0;
+	s = argv[2]; src.by.x = strtod(s, &s); src.by.y = strtod(s, &s); src.by.w = 0;
+
+	s = argv[3]; dst.p.x = strtod(s, &s); dst.p.y = strtod(s, &s); dst.p.w = strtod(s, &s);
+	s = argv[4]; dst.bx.x = strtod(s, &s); dst.bx.y = strtod(s, &s); dst.bx.w = 0;
+	s = argv[5]; dst.by.x = strtod(s, &s); dst.by.y = strtod(s, &s); dst.by.w = 0;
+
+	s = argv[6]; p.x = strtod(s, &s); p.y = strtod(s, &s); p.w = strtod(s, &s);
+
+	print("src\n\tp %v\n\tbx %v\n\tby %v\n", src.p, src.bx, src.by);
+	print("dst\n\tp %v\n\tbx %v\n\tby %v\n", dst.p, dst.bx, dst.by);
+	print("p  %v\n", p);
+	print("p' %v\n", rframexform(invrframexform(p, src), dst));
+//	print("S→D %v\n", rfxform(invrfxform(p, src), dst));
+//	print("D→S %v\n", rfxform(invrfxform(p, dst), src));
+//	print("S→ %v\n", invrfxform(p, src));
+//	print("→S %v\n", rfxform(p, src));
+//	print("D→ %v\n", invrfxform(p, dst));
+//	print("→D %v\n", rfxform(p, dst));
+
+	exits(nil);
+}