<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>图形验证码</title>
</head>
<style>
* {
padding:0;
margin:0;
}
.box {
width:300px;
height: 300px;
margin: 100px;
}
</style>
<body>
<div class="box">
<canvas id="canvas" width="300" height="90"></canvas>
</div>
</body>
<script type="text/javascript" charset="utf-8">
var canvas = document.getElementById("canvas");
/**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();
canvas.onclick = function() {
drawPic();
}
/**绘制验证码图片**/
function drawPic() {
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';
var yzm = '';
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(60, 80) + 'px SimHei'; //随机生成字体大小
var x = 30 + i * 60;
var y = randomNum(60, 90);
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);
yzm = yzm + txt;
//恢复坐标原点和旋转角度
ctx.rotate(-deg * Math.PI / 180);
ctx.translate(-x, -y);
}
canvas.className = yzm;
/**绘制干扰线**/
for (var i = 0; i < 3; i++) {
ctx.strokeStyle = randomColor(40, 280);
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 < 30; 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>
