标签：
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>Document</title>
</head>
<body>
<div id="console"></div>
<canvas id="canvas" width="960" height="400"></canvas>
<button onclick="exportImg(this)">导出图片</button>
线宽:
<select id="lineWidth" style="padding:6px;">
<option>1</option>
<option>2</option>
<option>4</option>
<option>5</option>
<option>8</option>
<option>10</option>
<option>12</option>
<option>16</option>
</select>
线颜色
<select id="lineColor" style="padding:6px;">
<option>red</option>
<option>yellow</option>
<option>blue</option>
<option>white</option>
</select>
<img src="" id="target" width="480" height="200"/>
</select>
<script type="text/javascript">
/**
技术：画板
技术点：html5 -canvas
开始工具：editplus+浏览器
步骤:
canvas/svg--flash
1:定义个canvas元素
2:画线
3:导出图片
*/
//获取画布对象
var canvaDom = document.getElementById("canvas");
//初始化画板的上下文
var context = canvaDom.getContext("2d");
//初始化画布的背景色
context.fillStyle = "black";
//画板的范围
//context.fillRect(x,y,width.height);
context.fillRect(0,0,960,400);
//添加鼠标事件
//a:鼠标按下去的事件
canvaDom.addEventListener("mousedown",down,false);
//b:鼠标移动事件
canvaDom.addEventListener("mousemove",draw,false);
//c:鼠标松开事件
canvaDom.addEventListener("mouseup",up,false);
//锁定开关
//event是javascript为每一个事件提供一个顶级类
var onoff = false;
var oldx = -10;
var oldy = -10;
var lineWidth = 1;
var lineColor = "red";
function down(event){
lienWidth = document.getElementById("lineWidth").value;
lineColor = document.getElementById("lineColor").value;
onoff = true;//锁定
//获取当前鼠标在画板中点击的x,y轴的坐标
oldx = event.clientX-10;
oldy = event.clientY-10;
document.getElementById("console").innerHTML = "x:="+oldx+";y:="+oldy;
}
//移动
function draw(event){
if(onoff){//开关
var newx = event.clientX-10;
var newy = event.clientY-10;
//核心---画线
context.beginPath();
//线的起始点坐标
context.moveTo(oldx,oldy);
context.lineTo(newx,newy);
//线的宽度
context.lineWidth = lienWidth;
//线的粗细(形状)
context.lineCap ="round";
//线的颜色
context.strokeStyle=getRandomColor();
//初始化到画布中
context.stroke();
oldx = newx;
oldy = newy;
}
}
function up(){
onoff = false;
}
/**/
function getRandomColor() {
return ‘#‘ + (function(h) {
return new Array(7 - h.length).join("0") + h;
})((Math.random() * 0x1000000 << 0).toString(16));
};
//导出图片
function exportImg(){
//初始画板的图片信息
var exportImg = canvas.toDataURL("image/png");
document.getElementById("target").src = exportImg;
}
</script>
</body>
</html>
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原文地址：http://www.cnblogs.com/qiyc/p/5925121.html
