drawwedge.as

AS3的画图功能一些源码

/*-------------------------------------------------------------
	mc.drawWedge is a method for drawing pie shaped
	wedges. Very useful for creating charts. Special
	thanks to: Robert Penner, Eric Mueller and Michael
	Hurwicz for their contributions.
-------------------------------------------------------------*/
MovieClip.prototype.drawWedge = function(x, y, startAngle, arc, radius, yRadius) {
	// ==============
	// mc.drawWedge() - by Ric Ewing ([e-mail]) - version 1.3 - 6.12.2002
	//
	// x, y = center point of the wedge.
	// startAngle = starting angle in degrees.
	// arc = sweep of the wedge. Negative values draw clockwise.
	// radius = radius of wedge. If [optional] yRadius is defined, then radius is the x radius.
	// yRadius = [optional] y radius for wedge.
	// ==============
	// Thanks to: Robert Penner, Eric Mueller and Michael Hurwicz for their contributions.
	// ==============
	if (arguments.length<5) {
		return;
	}
	// move to x,y position
	this.moveTo(x, y);
	// if yRadius is undefined, yRadius = radius
	if (yRadius == undefined) {
		yRadius = radius;
	}
	// Init vars
	var segAngle, theta, angle, angleMid, segs, ax, ay, bx, by, cx, cy;
	// limit sweep to reasonable numbers
	if (Math.abs(arc)>360) {
		arc = 360;
	}
	// Flash uses 8 segments per circle, to match that, we draw in a maximum
	// of 45 degree segments. First we calculate how many segments are needed
	// for our arc.
	segs = Math.ceil(Math.abs(arc)/45);
	// Now calculate the sweep of each segment.
	segAngle = arc/segs;
	// The math requires radians rather than degrees. To convert from degrees
	// use the formula (degrees/180)*Math.PI to get radians.
		theta = -(segAngle/180)*Math.PI;
	// convert angle startAngle to radians
	angle = -(startAngle/180)*Math.PI;
	// draw the curve in segments no larger than 45 degrees.
	if (segs>0) {
		// draw a line from the center to the start of the curve
		ax = x+Math.cos(startAngle/180*Math.PI)*radius;
		ay = y+Math.sin(-startAngle/180*Math.PI)*yRadius;
		this.lineTo(ax, ay);
		// Loop for drawing curve segments
		for (var i = 0; i<segs; i++) {
			angle += theta;
			angleMid = angle-(theta/2);
			bx = x+Math.cos(angle)*radius;
			by = y+Math.sin(angle)*yRadius;
			cx = x+Math.cos(angleMid)*(radius/Math.cos(theta/2));
			cy = y+Math.sin(angleMid)*(yRadius/Math.cos(theta/2));
			this.curveTo(cx, cy, bx, by);
		}
		// close the wedge by drawing a line to the center
		this.lineTo(x, y);
	}
};