用Canvas生成随机验证码(后端前端都可以)
时间：08-08来源：作者：点击数：
用Canvas生成随机验证码(后端前端都可以)
一 、使用前端生成验证码
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<canvas id="canvas" width="120" height="40"></canvas>
<a href="#" id="changeImg">看不清，换一张</a>
<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>
</body>
</html>
二、后端生成验证码
暂时这个
<html>
<meta http-equiv="X-UA-Compatible" content="chrome=1">
<head>
<script>
window.onload = function() {
draw();
var saveButton = document.getElementById("saveImageBtn");
bindButtonEvent(saveButton, "click", saveImageInfo);
var dlButton = document.getElementById("downloadImageBtn");
bindButtonEvent(dlButton, "click", saveAsLocalImage);
};
function draw(){
var canvas = document.getElementById("thecanvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "rgba(125, 46, 138, 0.5)";
ctx.fillRect(25,25,100,100);
ctx.fillStyle = "rgba( 0, 146, 38, 0.5)";
ctx.fillRect(58, 74, 125, 100);
ctx.fillStyle = "rgba( 0, 0, 0, 1)"; // black color
ctx.fillText("Gloomyfish - Demo", 50, 50);
}
function bindButtonEvent(element, type, handler)
{
if(element.addEventListener) {
element.addEventListener(type, handler, false);
} else {
element.attachEvent('on'+type, handler);
}
}
function saveImageInfo ()
{
var mycanvas = document.getElementById("thecanvas");
var image = mycanvas.toDataURL("image/png");
var w=window.open('about:blank','image from canvas');
w.document.write("<img src='"+image+"' alt='from canvas'/>");
}
function saveAsLocalImage () {
var myCanvas = document.getElementById("thecanvas");
// here is the most important part because if you dont replace you will get a DOM 18 exception.
// var image = myCanvas.toDataURL("image/png").replace("image/png", "image/octet-stream;Content-Disposition: attachment;filename=foobar.png");
var image = myCanvas.toDataURL("image/png").replace("image/png", "image/octet-stream");
window.location.href=image; // it will save locally
}
</script>
</head>
<body bgcolor="#E6E6FA">
<div>
<canvas width=200 height=200 id="thecanvas"></canvas>
<button id="saveImageBtn">Save Image</button>
<button id="downloadImageBtn">Download Image</button>
</div>
</body>
</html>
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