关于纯JS构建验证码背景图

Posted on 2019-11-15 14:17 闪电龟龟阅读(571) 评论(0) 编辑收藏举报

下面的内容均摘自https://www.cnblogs.com/zh-1721342390/p/9370794.html，如果想要了解详细，请到原文查看(PS:记得给博主点赞哦哦哦哦哦哦)

好处：减轻后端生成图片和传输过程的流量的传递，只获取验证码的数据，构建图片过程在客户端进行。

JS:

function drawCode(ImageCode) {
    var str = '';
    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 < 4; i++) {
        rand.push(rand[i]);
        rand[i] = ImageCode.charAt(i);
        x[i] = i * 20 + 10;
        y[i] = Math.random() * 20 + 20;
        context.fillText(rand[i], x[i], y[i]);
    }
    str = rand.join('').toUpperCase();
    //画3条随机线
    for (var i = 0; i < 20; 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 = getBackgroud(0.1); //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.strokeStyle = getBackgroud(0.1);
    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;
}
// 生成随机背景
function getBackgroud(Transparency) {
    var RColor = 255 * Math.random();
    var GColor = 255 * Math.random();
    var BColor = 255 * Math.random();
    return "rgba(" + RColor + ", " + GColor + ", " + BColor + ", " + Transparency + ")";
}

aspx：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="DeleteWebAPI.Default" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <%-- 根据验证码构建验证码图片 --%>
    <div id="verificationCode">
        <canvas width="100" height="40" id="verifyCanvas"></canvas>
        <img id="code_img" />
    </div>
    <script type="text/javascript" src="Script/jquery-3.4.1.min.js"></script>
    <script type="text/javascript" src="Script/ImageCode.js"></script>
    <script type="text/javascript">
        $(function () {
            $.ajax({
                url: "/api/Default/ImageCode",
                type: "get",
                contentType: "application/json",
                success: function (data) {
                    //console.log(data["Result"]);
                    drawCode(data["Result"]);  // 获取传递过来的验证码信息
                },
                error: function (xmlRequest) {
                    alert(xmlRequest.responseText);
                }
            });
        });
    </script>
</body>
</html>

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