Javascript HTML5 Canvas实现的一个画板

前端技术 2023/09/05 JavaScript

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>

以上就是本文的全部内容，希望对大家的学习有所帮助。

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