效果如图所示：
前提要下载jquery.min.js文件(百度搜索下载即可)
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>图形验证码</title>
<style>
.input-val {
width: 200px;
height: 32px;
border: 1px solid #ddd;
box-sizing: border-box;
}
#canvas {
vertical-align: middle;
box-sizing: border-box;
border: 1px solid #ddd;
cursor: pointer;
}
.btn {
display: block;
margin-top: 20px;
height: 32px;
width: 100px;
font-size: 16px;
color: #fff;
background-color: #457adb;
border: none;
border-radius: 50px;
}
</style>
<!-- 将这里的jquery文件换成自己的地址即可 -->
<script type="text/javascript" src="./jquery.min.js" ></script>
<script>
$(function(){
var show_num = [];
draw(show_num);
$("#canvas").on('click',function(){
draw(show_num);
})
$(".btn").on('click',function(){
var val = $(".input-val").val().toLowerCase();
var num = show_num.join("");
if(val==''){
alert('请输入验证码！');
}else if(val == num){
alert('提交成功！');
$(".input-val").val('');
// draw(show_num);
}else{
alert('验证码错误！请重新输入！');
$(".input-val").val('');
// draw(show_num);
}
})
})
//生成并渲染出验证码图形
function draw(show_num) {
var canvas_width=$('#canvas').width();
var canvas_height=$('#canvas').height();
var canvas = document.getElementById("canvas");//获取到canvas的对象，演员
var context = canvas.getContext("2d");//获取到canvas画图的环境，演员表演的舞台
canvas.width = canvas_width;
canvas.height = canvas_height;
var sCode = "a,b,c,d,e,f,g,h,i,j,k,m,n,p,q,r,s,t,u,v,w,x,y,z,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";
var aCode = sCode.split(",");
var aLength = aCode.length;//获取到数组的长度
for (var i = 0; i < 4; i++) { //这里的for循环可以控制验证码位数（如果想显示6位数，4改成6即可）
var j = Math.floor(Math.random() * aLength);//获取到随机的索引值
// var deg = Math.random() * 30 * Math.PI / 180;//产生0~30之间的随机弧度
var deg = Math.random() - 0.5; //产生一个随机弧度
var txt = aCode[j];//得到随机的一个内容
show_num[i] = txt.toLowerCase();
var x = 10 + i * 20;//文字在canvas上的x坐标
var y = 20 + Math.random() * 8;//文字在canvas上的y坐标
context.font = "bold 23px 微软雅黑";
context.translate(x, y);
context.rotate(deg);
context.fillStyle = randomColor();
context.fillText(txt, 0, 0);
context.rotate(-deg);
context.translate(-x, -y);
}
for (var i = 0; i <= 5; i++) { //验证码上显示线条
context.strokeStyle = randomColor();
context.beginPath();
context.moveTo(Math.random() * canvas_width, Math.random() * canvas_height);
context.lineTo(Math.random() * canvas_width, Math.random() * canvas_height);
context.stroke();
}
for (var i = 0; i <= 30; i++) { //验证码上显示小点
context.strokeStyle = randomColor();
context.beginPath();
var x = Math.random() * canvas_width;
var y = Math.random() * canvas_height;
context.moveTo(x, y);
context.lineTo(x + 1, y + 1);
context.stroke();
}
}
//得到随机的颜色值
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 + ")";
}
</script>
</head>
<body>
<div class="code">
<input type="text" value="" placeholder="请输入验证码（不区分大小写）" class="input-val">
<canvas id="canvas" width="100" height="30"></canvas>
<button class="btn">提交</button>
</div>
</body>
</html>