javascript实现画板功能

本文实例为大家分享了javascript实现画板功能的具体代码，供大家参考，具体内容如下

画板功能的实现

<!DOCTYPE html>
<html>
 <head>
 <meta charset="utf-8">
 <title></title>
 <style type="text/css">
 *{
 margin: 0;
 padding: 0;
 list-style: none;
 }

 body{
 background:url(11.jpg) 0 0 no-repeat;
 }

 .wrapper{
 margin: 10px;
 }

 .wrapper canvas{
 border: 1px solid blue;
 border-radius:25px;
 box-shadow: 10px 10px 5px brown;
 margin-bottom: 16px;
 background-color: #fff;

 }
 .wrapper .btn-list{
 width: 1000px;
 text-align: center;
 }

 .wrapper .btn-list li{
 display: inline-block;
 margin-left: 40px;

 }
 .wrapper .btn-list li input{
 background-color: darkgreen;
 color: blanchedalmond
 border: none;
 padding: 6px 13px;
 cursor: pointer;
 border-radius:25px;
 font-size: 18px;
 display: block;
 transition-duration: 0.2s;
 }

 .wrapper .btn-list li input:hover{
 border: 1px solid chocolate;
 box-shadow: 0 12px 15px 0 rgba(0,0,0,0.5);
 }
 </style>
 </head>
 <body>
 <!-- div.wrapper>canvas+ul.btn-list>li*5>input -->

 <div class="wrapper">
 <canvas class="cavs" width="1000" height="500"></canvas>
 <ul class="btn-list">
 <li><input type="color" id="colorBoard" value="colorBoard"></li>
 <li><input type="button" id="cleanBoard" value="清屏"></li>
 <li><input type="button" id="eraser" value="橡皮"></li>
 <li><input type="button" id="rescind" value="撤销"></li>
 <li><input type="range" id="lineRuler" value="线条" min="1" max="30"></li>
 </ul>
 </div>
 </body>

 <script src="jquery-3.4.1.min.js"></script>
 <script>
 var drawingLineObj = {
 cavs:$('.cavs'),
 context:$('.cavs').get(0).getContext('2d'),
 colorBoard:$('#colorBoard'),
 cleanBoard:$('#cleanBoard'),
 arrImg:[],
 eraser:$("#eraser"),
 rescind:$('#rescind'),
 lineRuler:$('#lineRuler'),
 bool:false,
 init:function(){
 this.context.lineCap = 'round'; //线条起始与结尾样式
 this.context.lineJoin = 'round'; //转弯
 this.draw(); //画笔函数
 this.btnFn(); //按钮函数
 },  

 draw:function(){
 var cavs = this.cavs,
 self = this;
 var c_x = cavs.offset().left, //canvas离左边的距离
 c_y = cavs.offset().top; //canvas离上边的距离

 cavs.mousedown(function(e){
 e = e||window.event;
 self.bool = true;
 var m_x = e.pageX - c_x, //鼠标点距离减去canvas离左边的距离等于画布点
  m_y = e.pageY - c_y; //鼠标点距离减去canvas离上边的距离等于画布点
 self.context.beginPath();
  self.context.moveTo(m_x,m_y);//鼠标在画布上的点
 var imgData = self.context.getImageData(0,0,self.cavs[0].width,self.cavs[0].height);
 self.arrImg.push(imgData);
 //console.log(self.arrImg);

 })
 cavs.mousemove(function(e){
 if(self.bool){ //定义一把锁，防止鼠标移开滑动
 self.context.lineTo(e.pageX-c_x,e.pageY-c_y);
 self.context.stroke(); //绘制出路径
 }

 })
 cavs.mouseup(function(){
  self.context.closePath(); //结束自动闭合
 self.bool = false; //鼠标不移动时画笔断开

 })
 cavs.mouseleave(function(){
 self.context.closePath(); //结束自动闭合
 self.bool = false; //鼠标不移动时画笔断开

 }) 

 },
 btnFn:function(){
 var self = this;
 $('.btn-list').on('click',function(e){
 e = e||window.event;
 switch(e.target.id){ //target
 case 'cleanBoard':
 self.context.clearRect(0,0,self.cavs[0].width,self.cavs[0].height) //[0]
 break
 case 'eraser':
 self.context.strokeStyle = '#fff'
 break
 case 'rescind':
 if(self.arrImg.length>0){
 self.context.putImageData(self.arrImg.pop(),0,0);
 break
 } 

 }
 })
 this.colorBoard.change(function(e){ //当颜色变化时改变字体的颜色
 self.context.strokeStyle = $(this).val();
 })

 this.lineRuler.change(function(e){ //线条的变化值
 self.context.lineWidth = $(this).val();
 })

 }

 }
 drawingLineObj.init();

 </script>
</html>

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