html前端通过canvas生成验证码

<dd> ???????????????????????????<input type="text" class="input-yzm topAlign" id="verify" name="verify" maxlength="5" autocomplete="off" placeholder="验证码" required> ???????????????????????????????<span class="span-yzm"> ?????????????????????????????????????<!--验证码--> ???????????????????????????????????? <canvas width="100" height="40" id="verifyCanvas"></canvas> ?????????????????????????????????????<img id="code_img"> ???????????????????????????????</span> ???????????????????????????</dd>

<!--验证码代码--><script type="text/javascript"> ???var nums = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "0", ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘, ‘G‘, ‘H‘, ‘I‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ???????‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘, ‘j‘, ‘k‘, ‘l‘, ‘m‘, ‘n‘, ‘o‘, ‘p‘, ‘q‘, ‘r‘, ‘s‘, ‘t‘, ‘u‘, ‘v‘, ‘w‘, ‘x‘, ???????‘y‘, ‘z‘]; ???drawCode(); ???// 绘制验证码 ???function drawCode() { ???????var canvas = document.getElementById("verifyCanvas"); ?//获取HTML端画布 ???????var context = canvas.getContext("2d"); ????????????????//获取画布2D上下文 ???????context.fillStyle = "cornflowerblue"; ?????????????????//画布填充色 ???????context.fillRect(0, 0, canvas.width, canvas.height); ??//清空画布 ???????context.fillStyle = "white"; ??????????????????????????//设置字体颜色 ???????context.font = "25px Arial"; ??????????????????????????//设置字体 ???????var rand = new Array(); ???????var x = new Array(); ???????var y = new Array(); ???????for (var i = 0; i < 5; i++) { ???????????rand[i] = nums[Math.floor(Math.random() * nums.length)] ???????????x[i] = i * 16 + 10; ???????????y[i] = Math.random() * 20 + 20; ???????????context.fillText(rand[i], x[i], y[i]); ???????} ???????//画3条随机线 ???????for (var i = 0; i < 3; i++) { ???????????drawline(canvas, context); ???????} ???????// 画30个随机点 ???????for (var i = 0; i < 30; i++) { ???????????drawDot(canvas, context); ???????} ???????convertCanvasToImage(canvas) ???} ???// 随机线 ???function drawline(canvas, context) { ???????context.moveTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); ????????????//随机线的起点x坐标是画布x坐标0位置，y坐标是画布高度的随机数 ???????context.lineTo(Math.floor(Math.random() * canvas.width), Math.floor(Math.random() * canvas.height)); ?//随机线的终点x坐标是画布宽度，y坐标是画布高度的随机数 ???????context.lineWidth = 0.5; ?????????????????????????????????????????????????//随机线宽 ???????context.strokeStyle = ‘rgba(50,50,50,0.3)‘; ??????????????????????????????//随机线描边属性 ???????context.stroke(); ????????????????????????????????????????????????????????//描边，即起点描到终点 ???} ???// 随机点(所谓画点其实就是画1px像素的线，方法不再赘述) ???function drawDot(canvas, context) { ???????var px = Math.floor(Math.random() * canvas.width); ???????var py = Math.floor(Math.random() * canvas.height); ???????context.moveTo(px, py); ???????context.lineTo(px + 1, py + 1); ???????context.lineWidth = 0.2; ???????context.stroke(); ???} ???// 绘制图片 ???function convertCanvasToImage(canvas) { ???????document.getElementById("verifyCanvas").style.display = "none"; ???????var image = document.getElementById("code_img"); ???????image.src = canvas.toDataURL("image/png"); ???????return image; ???} ???// 点击图片刷新 ???document.getElementById(‘code_img‘).onclick = function () { ???????$(‘#verifyCanvas‘).remove(); ???????$(‘#verify‘).after(‘<canvas width="100" height="40" id="verifyCanvas"></canvas>‘) ???????drawCode(); ???}</script>