绘制微信小程序验证码功能的实例代码_js教程

1.在 utils 文件中新建 mcaptcha.js 文件，写入以下代码：

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									module.exports = class Mcaptcha {

									  //画板

									 constructor(options) {

									  this.options = options;

									  this.fontSize = options.height * 3 / 4;

									  this.init();

									  this.refresh(this.options.code);

									 }

									 init() {

									  this.ctx = wx.createCanvasContext(this.options.el);

									  this.ctx.setTextBaseline("middle");

									  this.ctx.setFillStyle(this.randomColor(180, 240));

									  this.ctx.fillRect(0, 0, this.options.width, this.options.height);

									 }

									  //绘制彩图

									 refresh(code) {

									  let arr = (code + '').split('');

									  let width = this.options.width;

									  let height = this.options.height;

									  let ctx = this.ctx;

									  if (arr.length === 0) {

									   arr = ['e', 'r', 'r','o','r'];

									  };

									  let offsetLeft = width * 0.6 / (arr.length - 1);

									  let marginLeft = width * 0.2;

									  arr.forEach((item, index) => {

									   ctx.setFillStyle(this.randomColor(0, 180));

									   let size = this.randomNum(24, this.fontSize);

									   ctx.setFontSize(size);

									   let dis = offsetLeft * index + marginLeft - size * 0.3;

									   let deg = this.randomNum(-30, 30);

									   ctx.translate(dis, height*0.5);

									   ctx.rotate(deg * Math.PI / 180);

									   ctx.fillText(item, 0, 0);

									   ctx.rotate(-deg * Math.PI / 180);

									   ctx.translate(-dis, -height * 0.5);

									  })

									  //绘制干扰线

									  for (var i = 0; i < 2; i++) {

									      ctx.strokeStyle = this.randomColor(40, 180);

									      ctx.beginPath();

									      ctx.moveTo(this.randomNum(0, width), this.randomNum(0, height));

									      ctx.lineTo(this.randomNum(20, width), this.randomNum(2, height));

									      ctx.stroke();

									  }

									  //绘制干扰点

									  for (var i = 0; i < 30; i++) {

									      ctx.fillStyle = this.randomColor(0, 255);

									      ctx.beginPath();

									      ctx.arc(this.randomNum(0, width), this.randomNum(0, height), 1, 0, 2 * Math.PI);

									      ctx.fill();

									     }

									  ctx.draw();

									 }

									  //设置随机数的颜色

									 randomNum(min, max) {

									  return Math.floor(Math.random() * (max - min) + min);

									 }

									 randomColor(min, max) {

									  let r = this.randomNum(min, max);

									  let g = this.randomNum(min, max);

									  let b = this.randomNum(min, max);

									  return "rgb(" + r + "," + g + "," + b + ")";

									 }

									}

2.在需要验证码的js文件中引入

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									let Mcaptcha = require("../../../utils/mcaptcha.js");

res.data 是要传到mcaptcha.js 中的 code 值，也就是验证码，可以随意写为如：“ho55”，“a2sd” 等等。我这里是从后台传过来的数据，（前人写的代码，不好改动，只在前端加上干扰线和彩图）。

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									new Mcaptcha({

									  el: 'canvas',

									  width: 100,

									  height: 30,

									  code: res.data

									});

wxml 文件， bindtap="getImgYZM" 是 new Mcaptcha 的方法名，再次点击可以换验证码图片。

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									<view bindtap="getImgYZM" class="yzm">

									  <canvas style="width:{{cvs.width}};height:{{cvs.height}};" canvas-id="canvas"></canvas>

									</view>

如果是在前端设置随机数，可以在data:{} 里面写

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									data: {

									   str:"0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z",

									   randStr:""

									 }

									//获取随机数

									var res = "";

									for(var i = 0; i < str.length ; i ++) {

									  var id = Math.ceil(Math.random()*35);

									  res += chars[id];

									}

									return res;

这一步可不看，以下是后端C#语言产生随机数返给前端的代码：

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									using JobClass;

									using System;

									using System.Collections.Generic;

									using System.Drawing;

									using System.Linq;

									using System.Web;

									using System.Web.SessionState;

									namespace WebSite.pcode

									{

									  /// <summary>

									  /// getcode 的摘要说明

									  /// </summary>

									  public class getcode : IHttpHandler, IRequiresSessionState

									  {

									    public void ProcessRequest(HttpContext context)

									    {

									      context.Response.ContentType = "text/plain";

									      string str = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,Q,R,S,T,U,V,W,X,Y,Z";

									      string randStr = "";

									      //生成随机数 Random

									      Random randobj = new Random();

									      string[] arr = str.Split(',');

									      for (int i = 0; i < 4; i++)

									      {

									        randStr += arr[randobj.Next(arr.Length)];

									      }

									      context.Response.Write(randStr);

									      return;

									    }

									    public bool IsReusable

									    {

									      get

									      {

									        return false;

									      }

									    }

									  }

									}