Init

usr.lib/libplot/imagen/arc.c

@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 1985 Regents of the University of California.
+ * All rights reserved.  The Berkeley software License Agreement
+ * specifies the terms and conditions for redistribution.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)arc.c 1.1 94/10/31 SMI"; /* from UCB 5.1 9/21/85 */
+#endif not lint
+
+int del = 20;
+step(d){
+	del = d;
+}
+arc(x,y,x0,y0,x1,y1){
+	double pc;
+	double sqrt();
+	int flg,m,xc,yc,xs,ys,qs,qf;
+	float dx,dy,r;
+	char use;
+	dx = x-x0;
+	dy = y-y0;
+	r = dx*dx+dy*dy;
+	pc = r;
+	pc = sqrt(pc);
+	flg = pc/4;
+	if(flg == 0)step(1);
+	else if(flg < del)step(flg);
+	xc = xs = x0;
+	yc = ys = y0;
+	move(xs,ys);
+	if(x0 == x1 && y0 == y1)flg=0;
+	else flg=1;
+	qs = quad(x,y,x0,y0);
+	qf = quad(x,y,x1,y1);
+	if(abs(x-x1) < abs(y-y1)){
+		use = 'x';
+		if(qs == 2 || qs ==3)m = -1;
+		else m=1;
+	}
+	else {
+		use = 'y';
+		if(qs > 2)m= -1;
+		else m= 1;
+	}
+	while(1){
+		switch(use){
+		case 'x':	
+			if(qs == 2 || qs == 3)yc -= del;
+			else yc += del;
+			dy = yc-y;
+			pc = r-dy*dy;
+			xc = m*sqrt(pc)+x;
+			if((x < xs && x >= xc) || ( x > xs && x <= xc) ||
+			    (y < ys && y >= yc) || ( y > ys && y <=  yc) )
+			{
+				if(++qs > 4)qs=1;
+				if(qs == 2 || qs == 3)m= -1;
+				else m=1;
+				flg=1;
+			}
+			cont(xc,yc);
+			xs = xc; 
+			ys = yc;
+			if(qs == qf && flg == 1)
+				switch(qf){
+				case 3:
+				case 4:	
+					if(xs >= x1)return;
+					continue;
+				case 1:
+				case 2:
+					if(xs <= x1)return;
+				}
+			continue;
+		case 'y':	
+			if(qs > 2)xc += del;
+			else xc -= del;
+			dx = xc-x;
+			pc = r-dx*dx;
+			yc = m*sqrt(pc)+y;
+			if((x < xs && x >= xc) || ( x > xs && x <= xc ) ||
+			    (y < ys && y >= yc) || (y > ys && y <= yc) )
+			{
+				if(++qs > 4)qs=1;
+				if(qs > 2)m = -1;
+				else m = 1;
+				flg=1;
+			}
+			cont(xc,yc);
+			xs = xc; 
+			ys = yc;
+			if(qs == qf && flg == 1)
+				switch(qs){
+				case 1:
+				case 4:
+					if(ys >= y1)return;
+					continue;
+				case 2:
+				case 3:
+					if(ys <= y1)return;
+				}
+		}
+	}
+}
+quad(x,y,xp,yp){
+	if(x < xp)
+		if(y <= yp)return(1);
+		else return(4);
+	else if(x > xp)
+		if(y < yp)return(2);
+		else return(3);
+	else if(y < yp)return(2);
+	else return(4);
+}
+abs(a){
+	if(a < 0)return(-a);
+	return(a);
+}