s94-imgclip/vector.js

图片裁剪工具

(function(){
	"use strict";
	function Vector(x, y, z){
		if (arguments.length==1) {
			if(x instanceof Vector) return x;
			z = x.z;y = x.y;x = x.x;
		}
		if(!(this instanceof Vector)) return new Vector(x, y, z);
		this.x = x || 0;
		this.y = y || 0;
		this.z = z || 0;
	}
	var pro = {
		toString: function(){
			return "(" + ([this.x, this.y, this.z]).join(", ") + ")";
		},
		clone: function(){
			return new Vector(this.x, this.y, this.z);
		},
		length: function(){
			var hypot = Math.hypot || function(a, b, c){return Math.sqrt(a*a+b*b+c*c); };
			return hypot(this.x, this.y, this.z);
		},
		unit: function(){//当前向量的单位向量
			return this.ratio(1/this.length());
		},
		add: function(v){//向量加 this + v
			v = new Vector(v);
			return new Vector(this.x+v.x, this.y+v.y, this.z+v.z);
		},
		subtract: function(v){//向量减 this - v
			v = new Vector(v);
			return new Vector(this.x-v.x, this.y-v.y, this.z-v.z);
		},
		ratio: function(n){//标量乘法(数乘)向量的倍数
			return new Vector(this.x*n, this.y*n, this.z*n);
		},
		multiply: function(n){//标量乘法(数乘)倍数
			return new Vector(this.x*n, this.y*n, this.z*n);
		},
		divide: function(n){//标量除法(数除) this / n
			return new Vector(this.x/n, this.y/n, this.z/n);
		},
		dot: function(v){//数量积(点积、内积)向量v在当前向量方向上的投影长度与当前向量长度的乘积
			v = new Vector(v);
			return this.x*v.x + this.y*v.y + this.z*v.z;
		},
		cross: function(v){//向量积(叉积、外积)它的几何意义是所得的向量与被乘向量所在平面垂直，方向由右手定则规定，大小是两个被乘向量张成的平行四边形的面积
			v = new Vector(v);
			return new Vector(this.y*v.z - this.z*v.y, this.z*v.x - this.x*v.z, this.x*v.y - this.y*v.x);
		},
		//当前向量绕向量v旋转，具象表现为顺着向量v的方向，顺时针转动deg角度
		rotate: function(v, deg){
			v = new Vector(v);
			var vi = v.unit();
			//第一步、是对当前向量做正交分解，分解成平行于v的t1和垂直于v的t2两个向量
			var t1 = vi.ratio(this.dot(vi));
			var t2 = this.subtract(t1);
			//第二步、利用外积可以计算与t2和vi都垂直，且长度等于t2的向量t3
			var t3 = vi.cross(t2);
			//第三步、计算t2旋转deg角度后的向量t4
			var t4 = t2.ratio(Math.cos(deg)).add( t3.ratio(Math.sin(deg)) );
			//第三步、t4与t1相加得到当前向量旋转后的向量
			return t1.add(t4);
		},
	};
	for (var k in pro) {
		Object.defineProperty(Vector.prototype, k, {value: pro[k]});
	}
	
	module.exports = Vector;
})();