/**
* [html: <canvas id="pie1"></canvas>]
* [js: new Chart("pie1").ratePie(60);]
* author:zhengyong
* create:2016-05-11
*/
window.Chart=function(domId){
var canvas = document.getElementById(domId);
var ctx = canvas.getContext("2d");
var W = canvas.width;
var H = canvas.height;
var deg=0,new_deg=0,dif=0;
var text,text_w;
var R=W<H?W:H;//先默认环半径为canvas宽度
var bgR=(R-R/3)/2;//内环背景半径
var linkW=R/2-bgR;//环宽度=(W/2-内半径)
var inW=linkW/3;//内环宽度=环宽度*1/3
var outW=linkW*2/3;//外环宽度=环宽度*2/3
var inR=bgR+inW/2;//内环半径=内半径+内环宽度/2
var outR=bgR+inW+outW/2;//外环半径=内半径+内环宽度+外环宽度/2
var $this=this;
$this.ratePieNoAnimation=function(number){
deg=360*number/100;
//底色大
ctx.clearRect(0,0,W,H);
ctx.beginPath();
var grd = ctx.createLinearGradient(0,H, W, 0);//颜色渐变的起始坐标和终点坐标
grd.addColorStop(0, "#74DE1C");
grd.addColorStop(0.3, "#9DDE12");
grd.addColorStop(0.6, "#B2ED2E");
grd.addColorStop(1, "#CBF76C");
ctx.strokeStyle = grd;//生成的颜色块赋值给样式
ctx.lineWidth=outW;
ctx.arc(W/2,H/2,outR,0,Math.PI*2,false);
ctx.stroke();
//底色小
ctx.beginPath();
var grd = ctx.createLinearGradient(W, 0, 0,H);
grd.addColorStop(0, "#74DE1C");
grd.addColorStop(0.3, "#9DDE12");
grd.addColorStop(0.6, "#B2ED2E");
grd.addColorStop(1, "#CBF76C");
ctx.strokeStyle = grd;
ctx.lineWidth=inW;
ctx.arc(W/2,H/2,inR,0,Math.PI*2,false);
ctx.stroke();
//圆心背景
ctx.beginPath();
ctx.fillStyle="#D9E5E5";
ctx.arc(W/2,H/2,bgR,0,Math.PI*2,false);
ctx.fill();
//外层
var r = deg*Math.PI/180;
ctx.beginPath();
var grd = ctx.createLinearGradient(0,H, W, 0);
grd.addColorStop(0, "#8BEAF5");
grd.addColorStop(0.3, "#22A4D4");
grd.addColorStop(0.6, "#0B72BD");
grd.addColorStop(1, "#0A5DA0");
ctx.strokeStyle = grd;
ctx.lineWidth=outW;
ctx.arc(W/2,H/2,outR,0-90*Math.PI/180,r-90*Math.PI/180,false);
ctx.stroke();
//内层
ctx.beginPath();
var grd = ctx.createLinearGradient(W, 0, 0,H);
grd.addColorStop(0, "#8BEAF5");
grd.addColorStop(0.3, "#22A4D4");
grd.addColorStop(0.6, "#0B72BD");
grd.addColorStop(1, "#0A5DA0");
ctx.strokeStyle = grd;
ctx.lineWidth=inW;
ctx.arc(W/2,H/2,inR,0-90*Math.PI/180,r-90*Math.PI/180,false);
ctx.stroke();
ctx.fillStyle="#000";
ctx.font="bold "+R/4+"px Arial";
text = Math.floor(deg/360*100)+"%";
text_w = ctx.measureText(text).width;
ctx.fillText(text,W/2 - text_w/2,H/2+R/10);
};
$this.ratePie=function(number){
var i=0;
var t= setInterval(function(){
if(i==number){
clearInterval(t);
}else{
number>0?i++:i--;
}
$this.ratePieNoAnimation(i);
if(i > 100 || i < -100){//如果数字太大，取消动画效果
$this.ratePieNoAnimation(number);
clearInterval(t);
}
}, 2000/(number>0?number:-number));
}
}
