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>