Javascript HTML5 Canvas实现的一个画板

时间:2020-05-15 suvllian 人气:0

本文实例为大家分享了HTML5 Canvas实现的一个画板代码，供大家参考，具体内容如下

<!DOCTYPE html>
<html>
<head>
 <meta charset="utf-8">
 <title>DEMO6：自定义画板</title>
</head>
<body>
<canvas id="canvas" width="600" height="300">
 浏览器不支持canvas <!-- 如果不支持会显示这段文字 -->
</canvas>
<br/>
<button style="width:80px;background-color:yellow;" onclick='linecolor="yellow";'>YELLOW</button>
<button style="width:80px ;background-color:red;" onclick='linecolor="red";'>RED</button>
<button style="width:80px ;background-color:blue;" onclick='linecolor="blue";'>BLUE</button>
<button style="width:80px ;background-color:green;" onclick='linecolor="green";'>GREEN</button>
<button style="width:80px ;background-color:white;" onclick='linecolor="white";'>WHITE</button>
<button style="width:80px ;background-color:black;" onclick='linecolor="black";'>BLACK</button>
<br/>
 
<button style="width: 80px;background-color: white;" onclick="linw=4;">4PX</button>
<button style="width: 80px;background-color: white;" onclick="linw=8;">8PX</button>
<button style="width: 80px;background-color: white;" onclick="linw=16;">16PX</button>
<br/>
 
<button style="width: 80px;background-color: white;" onclick="copyimage();">EXPORT</button>
 
<br/>
<img src="" id="image_png" width="600px" height="300px">
<br/>
 
<script type="text/javascript">
 var canvas = document.getElementById('canvas'); //获取标签
 var ctx = canvas.getContext("2d"); 
 
 var fillStyle = "black";
 ctx.fillRect(0,0,600,300);
 var onoff = false; //按下标记
 var oldx = -10;
 var oldy = -10;
 //设置颜色
 var linecolor = "white";
 var linw = 4;
 canvas.addEventListener("mousemove",draw,true); //鼠标移动事件
 canvas.addEventListener("mousedown",down,false); //鼠标按下事件
 canvas.addEventListener("mouseup",up,false); //鼠标弹起事件
 function down(event){
  onoff = true;
  oldx = event.pageX - 10;
  oldy = event.pageY - 10;
 }
 function up(){
  onoff = false;
 }
 function draw(event){
  if (onoff==true) {
   var newx = event.pageX - 10;
   var newy = event.pageY - 10
   ctx.beginPath();
   ctx.moveTo(oldx,oldy);
   ctx.lineTo(newx,newy);
   ctx.strokeStyle = linecolor;
   ctx.lineWidth = linw;
   ctx.lineCap = "round";
   ctx.stroke();
 
   oldx = newx;
   oldy = newy;
  }
 }
 function copyimage(event)
 {
  var img_png_src = canvas.toDataURL("image/png"); //将画板保存为图片格式的函数
  document.getElementById("image_png").src = img_png_src;
 }
  
 </script> 
</body>
</html>

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