/**
* 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_HEIGHT=3,MARGIN=160,HAND_TRUNCATION = WIDTH/10,
HOUR_HAND_TRUNCTION = WIDTH/10,NUMERAL_SPACING = 20,
RADIUS = WIDTH/2-MARGIN,HAND_RADIUS=RADIUS+NUMERAL_SPACING,
numerals = [1,2,3,4,5,6,7,8,9,10,11,12],
snapshotBtn = doc.getElementById("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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<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>canvas钟表</title>
<style>
body{
background: #ddd;
}
body{
background: #aaaaaa;
}
#canvas{
position: absolute;
left:10px;
top:1.5em;
margin:20px;
border: thin solid dodgerblue;
background: #fff;
}
#snapshotImg{
position: absolute;
display: none;
left: 10px;
top:1.5em;
margin:20px;
border: thin solid dodgerblue;
background: #fff;
}
</style>
</head>
<body>
<div id="controls">
<input type="button" id="snapshotBtn" value="快照"/>
</div>
<img id="snapshotImg"/>
<canvas id="canvas" width="500" height="300"></canvas>
</body>
<script src="clock.js"></script>
</html>
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