java web图形验证码
<!DOCTYPE html>
<head>
<title>新用户注册</title>
<style>
#box2{
margin-top:1.5%;
}
input {
border-left:none;
}
</style>
</head>
<body>
<div class="input-group" id="box2">
<span class="input-group-addon">图形验证码：</span>
<input type="tel" class="form-control" placeholder="请输入图形验证码" />
<span><canvas id="canvas" width="120" height="45"></canvas>
<a href="#" id="changeImg">看不清，换一张</a></span>
</div>
<script>
/**生成一个随机数**/
function randomNum(min,max){
return Math.floor( Math.random()*(max-min)+min);
}
/**生成一个随机色**/
function randomColor(min,max){
var r = randomNum(min,max);
var g = randomNum(min,max);
var b = randomNum(min,max);
return "rgb("+r+","+g+","+b+")";
}
drawPic();
document.getElementById("changeImg").onclick = function(e){
e.preventDefault();
drawPic();
}
/**绘制验证码图片**/
function drawPic(){
var canvas=document.getElementById("canvas");
var width=canvas.width;
var height=canvas.height;
var ctx = canvas.getContext('2d');
ctx.textBaseline = 'bottom';
/**绘制背景色**/
ctx.fillStyle = randomColor(180,240); //颜色若太深可能导致看不清
ctx.fillRect(0,0,width,height);
/**绘制文字**/
var str = 'ABCEFGHJKLMNPQRSTWXY123456789';
for(var i=0; i<4; i++){
var txt = str[randomNum(0,str.length)];
ctx.fillStyle = randomColor(50,160); //随机生成字体颜色
ctx.font = randomNum(15,40)+'px SimHei'; //随机生成字体大小
var x = 10+i*25;
var y = randomNum(25,45);
var deg = randomNum(-45, 45);
//修改坐标原点和旋转角度
ctx.translate(x,y);
ctx.rotate(deg*Math.PI/180);
ctx.fillText(txt, 0,0);
//恢复坐标原点和旋转角度
ctx.rotate(-deg*Math.PI/180);
ctx.translate(-x,-y);
}
/**绘制干扰线**/
for(var i=0; i<8; i++){
ctx.strokeStyle = randomColor(40,180);
ctx.beginPath();
ctx.moveTo( randomNum(0,width), randomNum(0,height) );
ctx.lineTo( randomNum(0,width), randomNum(0,height) );
ctx.stroke();
}
/**绘制干扰点**/
for(var i=0; i<100; i++){
ctx.fillStyle = randomColor(0,255);
ctx.beginPath();
ctx.arc(randomNum(0,width),randomNum(0,height), 1, 0, 2*Math.PI);
ctx.fill();
}
}
</script>
</html>