^;^ 失落的微点

package com.foxaweb.pageflip {
 
	import flash.geom.Point;
	import flash.display.BitmapData;
	import flash.geom.Matrix;
	import flash.display.Shape;
 
             /**
	 * Computes, generates, and draws a pageflip.
	 * 
	 * @notice	PageFlip drawer
	 * @author	Foxy
	 * @version	1.0
	 * @date	2007-01-18
	 * 
	 * Original author :
	 * -----------------
	 * Didier Brun aka Foxy
	 * webmaster@foxaweb.com
	 * http://www.foxaweb.com
	 *
	 * 	AUTHOR * *****************************************************************************
	 * 
	 * authorName : 	Didier Brun - www.foxaweb.com
	 * 	contribution : 	the original class
	 * 	date :			2007-01-18
	 * 
	 * 	VISIT www.byteArray.org
	 * 
	 *
	 * LICENSE ******************************************************************************
	 * 
	 * 	This class is under RECIPROCAL PUBLIC LICENSE.
	 * 	http://www.opensource.org/licenses/rpl.php
	 * 
	 * 	Please, keep this header and the list of all authors
	 * 
	 *
	 *
	 * Nomenclature	
	 * ------------
	 *
	 *    PT(0,0)                                           PT(1,0)
	 *   ---------------------------------------------------
	 *      |  <-------------------PW---------------------->  |
	 *      | ^ Offset(0,0)  x-->					       |
	 *      | |						                 |
	 *      | | y                                             |
	 *      | | |                                             |
	 *      | | |                                             |
	 *      | | V                                             |
	 *      | |              pPoints[]                        |
	 *      | |                                               |
	 *      | |                                               |
	 *      | |                                               |
	 *      | |                                          (T3) |
	 *      | PH                                           ---|
	 *      | |                                         --- /  
	 *      | |                                      ---   /   
	 *      | |                                   ---     /    
	 *      | |                                ---       /    
	 *      | |                             ---         /     
	 *      | |                          ---           /       
	 *      | |                    PTD  --- cPoints[] /                                           
	 *      | |                         \            /         
	 *      | |                          \          /          
	 *      | |                           \        /           
	 *      | |                            \      /            
	 *      | |                             \    /             
	 *      | V                              \  /             
	 *      |-------------------------------- \/               
	 * PT(0,1)                                           PT(1,1)
	 */
	public class PageFlip {
 
 
		// ------------------------------------------------
		//
		// ---o public static methods
		//
		// ------------------------------------------------
 
		/**
		 * Compute and generate a new flip.
		 * 
		 * @param	ptd		Point indicating the position of the PTD point (the drag one) relative to the upper-left corner.
		 * @param	pt		Point indicating the original position of the dragged point. The two possible values for its x and y properties are 0 or 1. pt(0,0) is the upper-left corner, for example, pt (1,1) is the bottom-right one.
		 * @param	pw		int indicating the sheet width in pixels.
		 * @param	ph		int indicating the sheet height in pixels.
		 * @param	ish		If true, horizontal mode is provided, if false, vertical.
		 * @param	sens	Number indicating the constraints sensibility. This parametter is a multiplicator for the constraints values. It's intended to prevent some awefull flickering effects. Its possible value is ranged between 0.9 and 1. 0.9 -> when ptd move is free (drag'n'drop), 1 -> when ptd move is progresive (tween when release). At best, you should never swap it from .9 to 1. A progressive incrementation is better. If flickering effects don't disturb you or if your ptd moves is coded, keep this parametter to 1.
		 * 
		 * @return	Object containing:<br />
		 * 				cPoints:Array - Array of points which describes the flipped part of the sheet. Note that in case of the ptd point is aligned with its original position or if the height of the shape is very small (<1) this array is set to null.<br />
		 * 				pPoints:Array - Array of points wich describes the fixed part of the sheet.<br />
		 * 				matrix:Matrix - Transformation matrix for the flipped part of the sheet.<br />
		 * 				width:Number - Sheet width.<br />
		 * 				height:Number - Sheet height.
		 * 
		 */
		public static function computeFlip(ptd:Point,pt:Point,pw:int,ph:int,ish:Boolean,sens:int):Object{
 
			// useful vars
			var dfx:Number=ptd.x-pw*pt.x;
			var dfy:Number=ptd.y-ph*pt.y;
			var spt:Point=pt.clone();
			var opw:int=pw;
			var oph:int=ph;
 
			// offset corections
			var temp:Number;
 
			// transform matrix 
			var mat:Matrix=new Matrix();
 
			if (!ish){
				// size
				temp=pw;
				pw=ph;
				ph=temp;
 
				// ptd
				temp=ptd.x;
				ptd.x=ptd.y;
				ptd.y=temp;
 
				// pt
				temp=pt.x;
				spt.x=pt.y;
				spt.y=temp;
			}
 
			//	pt1 & pt2 are the two fixed points of the sheet. opposed to ptd drag one.
			var pt1:Point=new Point(0,0);
			var pt2:Point=new Point(0,ph);
 
			// default points array
			// cPoints -> the fliped part
			var cPoints:Array=[null,null,null,null];
			// pPoints -> the fixed part
			var pPoints:Array=[new Point(0,0),new Point(pw,0),null,null,new Point(0,ph)];
 
			// compute some flip
			flipDrag(ptd,spt,pw,ph);
 
			// ditstance 
			// it allows you to have a valid position for ptd.
			// the limit is the diagonal of the sheet here
			limitPoint(ptd,pt1,(pw*pw+ph*ph)*sens);
			// the limit is about the opposite fixed point
			limitPoint(ptd,pt2,(pw*pw)*sens);
 
			// first fliped point
			cPoints[0]=new Point(ptd.x,ptd.y);
 
			var dy:Number=pt2.y-ptd.y;
			var tot:Number=pw-ptd.x-pt1.x;
			var drx:Number=getDx(dy,tot);
 
			// fliped angle
			var theta:Number=Math.atan2(dy,drx);
			if (dy==0)theta=0;
 
			// another fliped angle
			var beta:Number=Math.PI/2-theta;
			var hyp:Number=(pw-cPoints[0].x)/Math.cos(beta);
 
			// vhyp is the hypotenuse of the fliped part
			var vhyp:Number=hyp;
			// if hyp is greater than the height of the sheet or hyp is 
			// negative, the fliped part has 4 points
			// else, it's just a 3 points part (simple corner).
			if (hyp>ph || hyp<0)vhyp=ph;
 
			// second fliped point
			cPoints[1]=new Point(	cPoints[0].x+Math.cos(-beta)*vhyp,
								cPoints[0].y+Math.sin(-beta)*vhyp);
 
			// last fliped point
			cPoints[3]=new Point(cPoints[0].x+drx,pt2.y);
 
			// if we have a 4 points shape
			if (hyp!=vhyp){
				dy=pt1.y-cPoints[1].y;
				tot=pw-cPoints[1].x;
				drx=getDx(dy,tot);
 
				// push the before the last point
				cPoints[2]=new Point(cPoints[1].x+drx,pt1.y);	
 
				// we can now find the fixed points of the sheet
				pPoints[1]=cPoints[2].clone();
				pPoints[2]=cPoints[3].clone();
				pPoints.splice(3,1);
			}else{
				// else we delete the point
				cPoints.splice(2,1);
 
				// we can now find the fixed points of the sheet
				pPoints[2]=cPoints[1].clone();
				pPoints[3]=cPoints[2].clone();
			}
 
			// these two polygons are always convex !
 
			// now we can flip the two arrays
			flipPoints(cPoints,spt,pw,ph);
			flipPoints(pPoints,spt,pw,ph);
 
			// if !ish (vertical mode)
			// we have to change the points orientation 
			if (!ish){
				oriPoints(cPoints,spt,pw,ph);
				oriPoints(pPoints,spt,pw,ph);
			}
 
			// flipped part transfrom matrix
 
			var gama:Number=theta;
 
			if (pt.y==0)gama=-gama;
			if (pt.x==0)gama=Math.PI+Math.PI-gama;
			if (!ish)gama=Math.PI-gama;
 
			mat.a=Math.cos(gama);
			mat.b=Math.sin(gama);
			mat.c=-Math.sin(gama);
			mat.d=Math.cos(gama);
 
			ordMatrix(mat,spt,opw,oph,ish,cPoints,pPoints,gama,beta);
 
			// here we fix some mathematical bugs or instabilities
			if (vhyp==0)cPoints=null;
			if (Math.abs(dfx)<1 && Math.abs(dfy)<1)cPoints=null;
 
			// now we just have to return all the stuff
			return {cPoints:cPoints,pPoints:pPoints,matrix:mat,width:opw,height:oph};
		}
 
		/**
		 * Draw a sheet using two Bitmap objects.
		 * 
		 * @param	ocf			computeFlip() returned object
		 * @param	mc			Target
		 * @param	bmp0		First page bitmap (left-top aligned)
		 * @param	bmp1		Second page bitmap (left-top aligned)
		 * 
		 */
		public static function drawBitmapSheet(ocf:Object,mc:Shape,bmp0:BitmapData,bmp1:BitmapData):void{
 
			// affectations
			var wid:Number=ocf.width;
			var hei:Number=ocf.height;
			var nb:Number;
			var ppts:Array=ocf.pPoints;
			var cpts:Array=ocf.cPoints;
 
 
			// draw the fixed part
			mc.graphics.beginBitmapFill(bmp0,new Matrix(),false,true);
			nb=ppts.length;
			mc.graphics.moveTo(ppts[nb-1].x,ppts[nb-1].y);
			while (--nb>=0)mc.graphics.lineTo(ppts[nb].x,ppts[nb].y);
			mc.graphics.endFill();
 
			// draw the flipped part
			if (cpts==null)return;
 
			mc.graphics.beginBitmapFill(bmp1,ocf.matrix,false,true);
			nb=cpts.length;
			mc.graphics.moveTo(cpts[nb-1].x,cpts[nb-1].y);
			while (--nb>=0)mc.graphics.lineTo(cpts[nb].x,cpts[nb].y);
			mc.graphics.endFill();
 
		}
 
		// ------------------------------------------------
		//
		// ---o private static methods
		//
		// ------------------------------------------------
 
		/**
		 * orientation correction
		 * @private
		 */
		private static function oriPoints(pts:Array,po:Point,pw:Number,ph:Number):void{
 
			var nb:Number=pts.length;
			var temp:Number;
 
			while (--nb>=0){
				temp=pts[nb].x;
				pts[nb].x=pts[nb].y;
				pts[nb].y=temp;
			}
		}
 
		/**
		 * ptdarg correction
		 * @private
		 */
		private static function flipDrag(ptd:Point,po:Point,pw:Number,ph:Number):void{
 
			// flip y
			if (po.y==0)ptd.y=ph-ptd.y;
 
			// flip x
			if (po.x==0)ptd.x=pw-ptd.x;
 
		}
 
		/**
		 * flip correction
		 * @private
		 */
		private static function flipPoints(pts:Array,po:Point,pw:Number,ph:Number):void{
 
			var nb:Number=pts.length;
			// flip
			if (po.y==0 || po.x==0){
				while (--nb>=0){
					if (po.y==0)pts[nb].y=ph-pts[nb].y;
					if (po.x==0)pts[nb].x=pw-pts[nb].x;
				}
			}
		}
 
		/**
		 * compute some trigonometry equation
		 * 
		 * this one is more stable than Math.atan2 for our case
		 * 
		 * @private
		 */
		private static function getDx(dy:Number,tot:Number):Number{
			return (tot*tot-dy*dy)/(tot*2);
		}
 
		/**
		 * limit the ptdrag position
		 * @private
		 */
		private static function limitPoint(ptd:Point,pt:Point,dsquare:Number):void{
 
			var theta:Number;
			var lim:Number;
 
			var dy:Number=ptd.y-pt.y;
			var dx:Number=ptd.x-pt.x;
 
			var dis:Number=dx*dx+dy*dy;
 
			// we save some times using square
			if (dis>dsquare){
				theta=Math.atan2(dy,dx);
				lim=Math.sqrt(dsquare);
				ptd.x=pt.x+Math.cos(theta)*lim;
				ptd.y=pt.y+Math.sin(theta)*lim;
			}
		}
 
		/**
		 * matric correction
		 * @private
		 */
		private static function ordMatrix(mat:Matrix,spt:Point,opw:Number,oph:Number,ish:Boolean,cPoints:Array,pPoint:Array,gama:Number,beta:Number):void{
 
			if (spt.x==1 && spt.y==0){
				mat.tx=cPoints[0].x;
				mat.ty=cPoints[0].y;
				if (!ish){
					mat.tx=cPoints[0].x-Math.cos(gama)*opw-Math.cos(-beta)*oph;
					mat.ty=cPoints[0].y-Math.sin(gama)*opw-Math.sin(-beta)*oph;
				}
			}
 
			if (spt.x==1 && spt.y==1){
				mat.tx=cPoints[0].x+Math.cos(-beta)*oph;
				mat.ty=cPoints[0].y+Math.sin(-beta)*oph;
				if (!ish){
					mat.tx=cPoints[0].x+Math.cos(-beta)*oph;
					mat.ty=cPoints[0].y-Math.sin(-beta)*oph;
				}
			}
 
			if (spt.x==0 && spt.y==0){
				mat.tx=cPoints[0].x-Math.cos(gama)*opw;
				mat.ty=cPoints[0].y-Math.sin(gama)*opw;
			}
 
			if (spt.x==0 && spt.y==1){
				mat.tx=cPoints[0].x-Math.cos(gama)*opw-Math.cos(-beta)*oph;
				mat.ty=cPoints[0].y-Math.sin(gama)*opw+Math.sin(-beta)*oph;
				if (!ish){
					mat.tx=cPoints[0].x;
					mat.ty=cPoints[0].y;
				}
			}
		}
	}
}