前面一篇介绍了《JS+HTML5 Canvas实现简单的写字板功能》，这里再介绍另一种实现方法。首先来看看运行效果：
具体代码如下：
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title> JS写字板</title> <style type="text/css"> #cans{ display: block; margin: 0 auto; } #selectColor{ margin: 0 auto; width: 400px; /* height: 50px;*/ text-align: center; margin-top: 10px; list-style: none; } .all{ /*width: 10%; height: 95%;*/ width: 60px; height: 50px; border: 1px solid #CCCCCC; float: left; margin-left: 10px; border-radius:6px ; cursor: pointer; } #red{ background-color: red; } #yellow{ background: yellow; } #black{ background: black; } #green{ background: green; } #blue{ background: #0000FF; } #clear{ margin-left: 10px; } #fontW{ width: 400px; margin: 0 auto; } </style> </head> <body> <canvas> 您的浏览器不支持该功能！ </canvas> <ul> <li></li> <li></li> <li></li> <li></li> <li></li> </ul></br> <input type="button" value="重画"> <!--<onclick="clears()">--> </br></br> <div> <strong>线条粗细：</strong>0<input type="range" min="0" max="20" onchange="changeW()" value="3"/>20 </div> <script type="text/javascript"> //初始化区 var ranges=document.getElementById("ranges"); var cans=document.getElementById("cans"); var clear=document.getElementById("clear"); cans.width=600; cans.height=600; var down=false; var up=false; var clears1=false; var lastmousePos={x:0,y:0}; var curmousePos={x:0,y:0}; var lastWidth; var curWidth=3; //设置canvas宽高 var CanvasWidth=cans.width; var CanvasHeight=cans.height; var half_width=CanvasWidth/2; var half_height=CanvasHeight/2; var frameW=10; var lineW=1; //改变线条宽度 function changeW(){ curWidth=ranges.value; } var drawCol="black"; //改变字体颜色 function changecolor(s){ drawCol=s; } var cts=cans.getContext("2d"); //设置米字格子 //开始绘制前设置基本样式 drawcanvs() function drawcanvs(){ cts.lineCap="round" cts.lineJoin="round" cts.lineWidth=frameW; cts.strokeStyle="red" cts.beginPath() cts.moveTo(0,0); cts.lineTo(CanvasWidth,0); cts.lineTo(CanvasWidth,CanvasHeight); cts.lineTo(0,CanvasHeight); cts.closePath() cts.stroke() //画x cts.lineWidth=lineW; cts.beginPath() cts.moveTo(0,0); cts.lineTo(CanvasWidth,CanvasHeight); cts.closePath() cts.stroke() cts.beginPath() cts.moveTo(CanvasWidth,0); cts.lineTo(0,CanvasHeight); cts.closePath() cts.stroke() cts.beginPath() cts.moveTo(half_width,0); cts.lineTo(half_width,CanvasHeight); cts.closePath() cts.stroke() cts.beginPath() cts.moveTo(0,half_height); cts.lineTo(CanvasWidth,half_height); cts.closePath() cts.stroke() } cans.onmousemove=function(e){ var e=e||event; var clx=e.clientX-cans.getBoundingClientRect().left;//将鼠标原点化为画布原点 var cly=e.clientY-cans.getBoundingClientRect().top; curmousePos={x:clx,y:cly}; if(down){ //开始画 //设置画笔颜色、粗细等 cts.lineCap="round" cts.lineJoin="round" cts.lineWidth=curWidth; cts.strokeStyle=drawCol; //开始绘画 cts.save(); cts.beginPath(); cts.moveTo(lastmousePos.x,lastmousePos.y); cts.lineTo(curmousePos.x,curmousePos.y); cts.closePath(); cts.stroke(); cts.restore(); lastmousePos=curmousePos; } if(up){ down=false; up=false; } } //鼠标按下事件 cans.onmousedown=function(e){ var e=e||event; e.preventDefault(); lastmousePos=curmousePos down=true; } //鼠标松开事件 cans.onmouseup=function(e){ var e=e||event; e.preventDefault(); up=true; } //计算速度 // function calV(s,t){ // var v=s/t; // if(v<0.1){ // curWidth=10; // }else if(v>10){ // curWidth=2; // }else{ // curWidth=5 // } // } function changeBg(){ var all=document.getElementsByClassName("all"); for(var i=0;i<all.length;i++){ all[i].onmouseover=function(){ this.style.cssText="margin-top:-6px;box-shadow:3px 5px 5px black" } all[i].onmouseout=function(){ this.style.cssText="border: 1px solid #CCCCCC;" } } } changeBg() //恢复原状 function ss(s){ s.style.cssText="margin-top:0px;box-shadow:none;" } //清除方法 clear.onmousedown=function (){ cts.clearRect(0,0,cans.width,cans.height); // clears1=true; } //清除后重画 clear.onmouseup=function(){ drawcanvs(); } </script> </body> </html>