#canvas实现登录的图形验证码

canvas实现登录的图形验证码

html部分的代码如下：

              <div class="s-canvas" >
                <input type="text" placeholder="请输入右侧四位随机码" v-model="randomCode">
                <canvas id="s-canvas" :width="contentWidth" :height="contentHeight" @click="createdCode"></canvas>
              </div>

通过props传递一些参数并设置数据类型，控制页面上图形验证码的一些样式，可以根据需求修改。

props: {
    fontSizeMin: {
      type: Number,
      default: 25
    },
    fontSizeMax: {
      type: Number,
      default: 30
    },
    backgroundColorMin: {
      type: Number,
      default: 255
    },
    backgroundColorMax: {
      type: Number,
      default: 255
    },
    colorMin: {
      type: Number,
      default: 0
    },
    colorMax: {
      type: Number,
      default: 160
    },
    lineColorMin: {
      type: Number,
      default: 100
    },
    lineColorMax: {
      type: Number,
      default: 255
    },
    dotColorMin: {
      type: Number,
      default: 0
    },
    dotColorMax: {
      type: Number,
      default: 255
    },
    contentWidth: {
      type: Number,
      default: 120
    },
    contentHeight: {
      type: Number,
      default: 40
    }
  },

在methods中写入一些有关函数，可以根据需求删除一些不需要的函数。

methods: {
    createdCode () { // 生成4个随机数
      const len = 4
      const codeList = []
      const chars = 'ABCDEFGHJKMNPQRSTWXYZ123456789'
      const charsLen = chars.length
      for (let i = 0; i < len; i++) {
        codeList.push(chars.charAt(Math.floor(Math.random() * charsLen)))
      }
      this.identifyCode = codeList.join('')
      this.$emit('getIdentifyCode', this.identifyCode.toLowerCase())
      this.drawPic()
    },
    randomNum (min, max) { // 生成一个随机数
      return Math.floor(Math.random() * (max - min) + min)
    },
    randomColor (min, max) { // 生成一个随机的颜色
      const r = this.randomNum(min, max)
      const g = this.randomNum(min, max)
      const b = this.randomNum(min, max)
      return 'rgb(' + r + ',' + g + ',' + b + ')'
    },
    drawPic () { // 绘制背景和颜色
      const canvas = document.getElementById('s-canvas')
      const ctx = canvas.getContext('2d')
      ctx.textBaseline = 'bottom'
      // 绘制背景
      ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax)
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
      // 绘制文字
      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i)
      }
      this.drawLine(ctx)
      this.drawDot(ctx)
    },
    drawText (ctx, txt, i) { // 倾斜文字
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
      ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
      const x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
      const y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
      var deg = this.randomNum(-45, 45)
      // 修改坐标原点和旋转角度
      ctx.translate(x, y)
      ctx.rotate(deg * Math.PI / 180)
      ctx.fillText(txt, 0, 0)
      // 恢复坐标原点和旋转角度
      ctx.rotate(-deg * Math.PI / 180)
      ctx.translate(-x, -y)
    },

    // 绘制干扰线
    drawLine (ctx) {
      for (let i = 0; i < 5; i++) {
        ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
        ctx.beginPath()
        ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
        ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
        ctx.stroke()
      }
    },

    // 绘制干扰点
    drawDot (ctx) {
      for (let i = 0; i < 80; i++) {
        ctx.fillStyle = this.randomColor(0, 255)
        ctx.beginPath()
        ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
        ctx.fill()
      }
    }
  },

　　在页面初始化时绘制图形验证码

  mounted () {
    this.createdCode()
  }