js+h5 canvas实现图片验证码

<div class="login_code_box">
        <div class="login_code">
         <input type="text" name="login_code" id="login_code" placeholder="请输入验证码">
                
 
        </div>
        <canvas id="canvas" >
 
        </canvas>
     <!-- <img src="" alt="" title="看不清？单击此处刷新" class="login_code_img" > -->
</div>

#canvas{
  width: 130px;
  height: 45px;
  display: inline-block;
  border: 1px solid #c9c9c9;
  border-radius: 5px;
  
}

//验证码生成
let canvas=document.getElementById('canvas')//画布对象
 
let show_num=[]//装验证码的数组
//产生随机颜色
function randomColor(){
  var r= Math.floor( Math.random()*256);
  var g= Math.floor( Math.random()*256);
  var b= Math.floor( Math.random()*256);
  return "rgb("+r+","+g+","+b+") "
}
//画布
function draw(show_num){
  let canvas_clientWidth=document.getElementById('canvas').clientWidth//画布长度
  let canvas_clientHeight=document.getElementById('canvas').clientHeight//画布高度
  let context = canvas.getContext("2d")//画布环境 创建 context 对象：
  canvas.width=canvas_clientWidth
  canvas.height=canvas_clientHeight
  let str="A,B,C,E,F,G,H,J,K,L,M,N,P,Q,R,S,T,W,X,Y,Z,1,2,3,4,5,6,7,8,9,0,q,w,e,r,t,y,u,i,o,p,a,s,d,f,g,h,j,k,l,z,x,c,v,b,n,m";
  let astr=str.split(',');//分割字符串形成数组
  let sLength=astr.length;//数组长度
  for (let i = 0; i <= 3; i++) {
    let j=Math.floor(Math.random()*sLength);//随机索引
    let deg=Math.random()*30*Math.PI/180;//0-30随机弧度
    let text=astr[j];//随机字符
    show_num[i]=text//验证码字符数组
    let x=10+i*20//x坐标
    let y=20+Math.random()*8//y坐标
    //位移 旋转角度 颜色 文字 样式开始位置
    context.font='bold 23px 微软雅黑'
    context.translate(x, y);
    context.rotate(deg);
    context.fillStyle = randomColor();
    context.fillText(text,0,0)
    context.rotate(-deg)
    context.translate(-x,-y)
  }
  //验证码显示小点
  for(let i=0;i<=30;i++){
   context.strokeStyle=randomColor()//设置随机色用小点的颜色
   context.beginPath();//开始一条路径
   let m=Math.random()*canvas_clientWidth;
   let n=Math.random()*canvas_clientHeight;
   context.moveTo(m,n)//移动
   context.lineTo(m + 1, n + 1);//添加一个新点，然后在画布中创建从该点到最后指定点的线条
   context.stroke();//画上面定义好的路径
  }
  //验证码显示线条
  for (let i = 0; i < 8; i++) {
    context.strokeStyle=randomColor()
    context.beginPath()
    context.moveTo(Math.random()*canvas_clientWidth,Math.random()*canvas_clientHeight);
    context.lineTo(Math.random()*canvas_clientWidth,Math.random()*canvas_clientHeight)
    context.stroke()
    
  }
 
}
draw(show_num)
console.log(show_num);
 
canvas.onclick=()=>{
draw(show_num)
console.log(show_num);
}