HTML5学习记录canvas学习之动画快照

/**
* Created by wsf on 2014-11-22.
*/
(function(win){
"use strict";
var doc = win.document,cvs = doc.getElementById("canvas"),ctx = cvs.getContext("2d"),
WIDTH = cvs.width,HEIGHT = cvs.height,
FONT_snapshotBtn"),
snapshotImg = doc.getElementById("snapshotImg"),
loop;
/**
* 画图函数
* @type {{}}
*/
var _functiOns= {
//画外层圆形
drawCircle:function(){
ctx.beginPath();//开始路径
ctx.arc(WIDTH/2,HEIGHT/2,RADIUS,0,Math.PI*2,true);
ctx.stroke();
},
//画钟表刻度
drawNumerals:function(){
var angle = 0,numeralWidth = 0;
numerals.forEach(function(numeral){
angle = Math.PI/6*(numeral-3);
numeralWidth = ctx.measureText(numeral).width;
ctx.fillText(numeral,WIDTH/2+Math.cos(angle)*(HAND_RADIUS)-numeralWidth/2,HEIGHT/2+Math.sin(angle)+(HAND_RADIUS)+FONT_HEIGHT/3);
});
},
//画中间圆心
drawCenter:function(){
ctx.beginPath();
ctx.arc(WIDTH/2,HEIGHT/2,5,0,Math.PI*2,true);
ctx.fill();//实心
},
//画钟表指针
drawHand:function(loc,isHour){
var angle = (Math.PI*2)*(loc/60)-Math.PI/ 2,
handRadius = isHour?RADIUS-HAND_TRUNCATION-HOUR_HAND_TRUNCTION:RADIUS-HAND_RADIUS;
ctx.moveTo(WIDTH/2,HEIGHT/2);//改变圆点坐标
ctx.lineTo(WIDTH/2+Math.cos(angle)*handRadius,HEIGHT/2+Math.sin(angle)*handRadius);
ctx.stroke();
},
//画所有的钟表指针
drawHands:function(){
var _d = new Date,_h = _d.getHours(),
_h = _h>12?_h-12:_h;
this.drawHand(_h*5+(_d.getMinutes()/60)*5,true);
this.drawHand(_d.getMinutes(),false);
this.drawHand(_d.getSeconds(),false);
},
//画钟表主函数
drawClock: function () {
ctx.clearRect(0,0,WIDTH,HEIGHT);//清空画布
this.drawCircle();
this.drawCenter();
this.drawHands();
//this.drawNumerals();
}
}
ctx.fOnt= FONT_HEIGHT+"px";
loop = setInterval(function(){
_functions.drawClock.call(_functions);
},1000);
/**
* 重点思路
* @param e
*/
snapshotBtn.Onclick= function(e){
var dataUrl;
if(snapshotBtn.value === "快照"){
dataUrl = cvs.toDataURL();//重点方法
clearInterval(loop);
snapshotImg.src = dataUrl;
snapshotImg.style.display = "inline";
cvs.style.display = "none";
snapshotBtn.value="恢复";
}else{
cvs.style.display = "inline";
snapshotImg.style.display = "none";
loop = setTimeout(function(){
_functions.drawClock.call(_functions);
},1000);
snapshotBtn.value="快照";
}
}
})(window);

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