微信小程序canvas2d生成图形验证码的方法
时间：2023-01-20 09:35:29 | 栏目：JavaScript代码 | 点击：次
本文实例为大家分享了微信小程序canvas2d生成图形验证码的具体代码，供大家参考，具体内容如下
成品展示：
背景：
大致看了一下网上已经有一些canvas生成图形验证码的demo，发现使用的也只是旧版canvas，相比于新版canvas2d性能上略有差距，更重要的是旧版canvas在开发者工具上报警告，非得整成canvas2d的不成。成果记录在此。
wxml：
<input class="input font_14" placeholder-class="grey" type="text"
placeholder="输入图形验证码" maxlength="4" model:value="{{guiCode}}"
bindinput="bindinput" />
<canvas class="guiCode" type="2d" id="guiCodeCanvas" bindtap="guiCodeTap" />
wxss：
.input {
width: calc(165vmin / 3.75);
height: 100%;
padding: 0 calc(12vmin / 3.75);
box-sizing: border-box;
}
.guiCode {
width: calc(70vmin / 3.75);
height: 100%;
}
js：
var guiCode = require('../../utils/guiCode.js');
const app = getApp()
Page({
data: {
guiCode: ''
},
onLoad: function (options) {
this.guiCode = new guiCode({
el: '#guiCodeCanvas',
width: 70,
height: 50,
createCodeImg: ""
})
},
bindinput() {},
/**
* 刷新图形验证码
*/
guiCodeTap() {
this.guiCode.refresh()
},
/**
* 验证图形验证码
*/
validateGuiCode() {
if (!this.data.guiCode) {
wx.showToast({
title: '请输入图形验证码',
icon: 'none'
})
return
}
let res = this.guiCode.validate(this.data.guiCode)
if (!res) {
wx.showToast({
title: '图形验证码错误',
icon: 'none'
})
}
},
/**
* 立即验证按钮监听
*/
toValidate() {
//验证图形验证码
this.validateGuiCode()
},
})
guiCode工具类：
module.exports = class guiCode {
constructor(options) {
this.options = options
this.init()
}
init() {
// 注意：如果在组件中使用，请将这里的 wx 改为 this
wx.createSelectorQuery().select(this.options.el)
.fields({
node: true,
size: true
}).exec((res) => {
this.canvas = res[0].node
this.ctx = this.canvas.getContext('2d')
this.canvas.width = this.options.width
this.canvas.height = this.options.height
this.fontSize = this.options.height * 3 / 6
this.ctx.textBaseline = "middle"
this.ctx.fillStyle = this.randomColor(180, 240)
this.refresh()
})
}
refresh() {
//清除上一次绘制
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height)
var code = ''
var txtArr = ['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', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
for (var i = 0; i < 4; i++) {
code += txtArr[this.randomNum(0, txtArr.length)]
}
this.options.createCodeImg = code
let arr = (code + '').split('')
if (arr.length === 0) {
arr = ['e', 'r', 'r', 'o', 'r']
}
let offsetLeft = this.options.width * 0.6 / (arr.length - 1)
let marginLeft = this.options.width * 0.2
arr.forEach((item, index) => {
this.ctx.fillStyle = this.randomColor(0, 180)
let size = this.randomNum(18, this.fontSize)
this.ctx.font = size + "px Arial"
let dis = offsetLeft * index + marginLeft - size * 0.3
let deg = this.randomNum(-30, 30)
this.ctx.translate(dis, this.options.height * 0.5)
this.ctx.rotate(deg * Math.PI / 180)
this.ctx.fillText(item, 0, 0)
this.ctx.rotate(-deg * Math.PI / 180)
this.ctx.translate(-dis, -this.options.height * 0.5)
})
for (var i = 0; i < 4; i++) {
this.ctx.strokeStyle = this.randomColor(40, 180)
this.ctx.beginPath()
this.ctx.moveTo(this.randomNum(0, this.options.width), this.randomNum(0, this.options.height))
this.ctx.lineTo(this.randomNum(0, this.options.width), this.randomNum(0, this.options.height))
this.ctx.stroke()
}
for (var i = 0; i < this.options.width / 4; i++) {
this.ctx.fillStyle = this.randomColor(0, 255)
this.ctx.beginPath()
this.ctx.arc(this.randomNum(0, this.options.width), this.randomNum(0, this.options.height), 1, 0, 2 * Math.PI)
this.ctx.fill()
}
}
validate(code) {
var code = code.toLowerCase()
var v_code = this.options.createCodeImg.toLowerCase()
if (code == v_code.substring(v_code.length - 4)) {
return true
} else {
return false
}
}
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 + ")"
}
}
至此就成功了。