前端图片验证码开发

先看下效果图：

这里是用canvas技术绘制，通过toDataURL方法将canvas画布转换成图片base64地址。

注明：vue框架开发，以下是html部分

<div class="get_code" @click="drawCode(\'\')" id="code">
                    <canvas width="100" height="40" id="verifyCanvas"></canvas>
                    <img id="code_img">
                </div>　　　　　　

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\'
],

// 绘制验证码
//代码中this指向vue的实例化对象

            drawCode(str) {
                document.getElementById(\'verifyCanvas\').remove();//每次更新验证码都要移除canvas，然后再进行重绘
                var box = document.getElementById("code");
                var p1 = document.getElementById("code_img");

                var p0 = document.createElement(\'canvas\');//创建canvas节点
                p0.id = \'verifyCanvas\';//定义canvas id

                box.insertBefore(p0, p1);//将canvas节点插入到img节点前面
                p0.width = 100;//设置画布宽度
                p0.height = 40;//设置画布高度
                var canvas = document.getElementById("verifyCanvas"); //获取HTML端画布
                var context = canvas.getContext("2d"); //获取画布2D上下文环境
                context.fillStyle = "#fff"; //画布填充色
                context.fillRect(0, 0, canvas.width, canvas.height); //清空画布
                context.fillStyle = "#800000"; //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] = this.nums[Math.floor(Math.random() * this.nums.length)]；//在数组中随机取一个值
                    x[i] = i * 20 + 10;
                    y[i] = Math.random() * 20 + 20;
                    context.fillText(rand[i], x[i], y[i]);//设置文本在画布中显示的位置
                }
                this.str = rand.join(\'\').toUpperCase();//将验证码的值中小写字母转为大写
                //画3条随机线
                for(var i = 0; i < 3; i++) {
                    this.drawline(canvas, context);
                }

                // 画30个随机点
                for(var i = 0; i < 30; i++) {
                    this.drawDot(canvas, context);
                }
                this.convertCanvasToImage(canvas);
                return this.str;
            },
            // 随机线
            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)
            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
            convertCanvasToImage(canvas) {
                document.getElementById("verifyCanvas").style.display = "none";
                var image = document.getElementById("code_img");
                image.src = canvas.toDataURL("image/png");//画布转成图片地址
                return image;//返回图片对象


            }