微信小程序验证码 绘制微信小程序验证码功能的实例代码
WALL*E 人气:01.在 utils 文件中新建 mcaptcha.js 文件，写入以下代码：
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
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）。
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。
<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
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：
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;
}
}
}
}
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