vue使用canvas手写输入识别中文

效果图：

前言：

最近做一个室外大屏项目，系统上的输入法使用不方便，客户要求做一个嵌入web网页的手写输入法。

核心：

后端接口api：使用 QQ输入法手写接口

https://handwriting.shuru.qq.com/cloud/cgi-bin/cloud_hw_pub.wsgi

注：此接口通过其他大佬文章获知，原文在此，本人未能查到官方文档相关地址，如果有大佬知晓还请留言告知，感谢！

思路：

（1）创建一个canvas绘图区域

// template
<div class="canvas-container">
 <canvas ref="canvas" width="300" height="200">你的浏览器不支持 canvas，请升级你的浏览器。</canvas>
</div>

// scss
.canvas-container {
 background: #fafafa;

 canvas {
 background: #fff;
  border: 1px solid #000;
 }
}

（2）获取初始横纵坐标

data() {
  return {
    initX: 0, // 初始横坐标
    initY: 0, // 初始纵坐标
  }
},
mounted() {
  this.initBound()
},
methods: {
  // 初始化canvas位置
  initBound() {
    let bound = this.$refs.canvas.getBoundingClientRect()
    this.initX = bound.x
    this.initY = bound.y
  }
}

（3）添加鼠标点击事件、移动事件、松开事件

// template
<div class="canvas-container">
 <canvas ref="canvas" width="300" height="200" @mousedown="onMouseDown" @mousemove="onMouseMove" @mouseup="onMouseUp">你的浏览器不支持 canvas，请升级你的浏览器。</canvas>
</div>
// script
data() {
  return {
    // ...

    lastX: 0, // 上一个横坐标
    lastY: 0, // 上一个纵坐标
    isHandWrite: false, // 是否开始手写
    pointsXY: [], // 单笔画
    allPointsXY: [], // 全部笔画
  }
},
methods: {
  onMouseDown(e) {
    this.pointsXY = []
    let cx = e.clientX - this.initX
    let cy = e.clientY - this.initY
    this.lastX = cx
    this.lastY = cy
    this.pointsXY.push(cx)
    this.pointsXY.push(cy)
    this.isHandWrite = true
  },
  onMouseMove(e) {
    if (this.isHandWrite) {
      let cx = e.clientX - this.initX
      let cy = e.clientY - this.initY
      this.pointsXY.push(cx - this.lastX)
      this.pointsXY.push(cy - this.lastY)
      // 获取2d上下文对象
      let ctx = this.$refs.canvas.getContext('2d')
      // 新建一条路径
      ctx.beginPath()
      ctx.strokeStyle = '#000'
      ctx.fillStyle = '#000'
      ctx.lineWidth = 8
      ctx.lineCap = 'round'
      ctx.moveTo(this.lastX, this.lastY)
      ctx.lineTo(cx, cy)
      ctx.stroke()
      this.lastX = cx
      this.lastY = cy
    }
  },
  onMouseUp(e) {
    if (this.isHandWrite) {
      this.isHandWrite = false
      this.allPointsXY.push(this.pointsXY.join(','))
      this.queryText() // 识别文字
    }
  },
}

（4）添加识别文字接口以及jsonp回调函数，跨域请求使用了 vue-jsonp ，具体用法可参vue中jsonp的使用方法

// script
data() {
  return {
    // ...

    write_result: [], // 返回相近字
  }
},
mounted() {
  // ...

  let _this = this
  // 添加jsonp回调函数, qq输入法特定
  window['QQShuru'] = {
    HWPanel: {
      ajax_callback: function (res) {
        _this.write_result = res.cand
      },
    },
  }
},
methods: {
  queryText() {
    let track_str = this.allPointsXY.join(',eb,')
    this.$jsonp(
      `https://handwriting.shuru.qq.com/cloud/cgi-bin/cloud_hw_pub.wsgi?track_str=${track_str}&cmd=0`
    ).catch(err => {
      console.log(err)
    })
  },
}

（5）最后再加个清除画布的重写按钮

// template
<div>
  <button @click="onReload">重写</button>
</div>

// script
onReload() {
  if (!this.$refs.canvas) return
  this.pointsXY = []
  this.allPointsXY = []
  let ctx = this.$refs.canvas.getContext('2d')
  ctx.clearRect(0, 0, 300, 200)
}

全部代码如下：

<template>
  <div id="app">
    <div class="canvas-container">
      <canvas ref="canvas" width="300" height="200" @mousedown="onMouseDown" @mousemove="onMouseMove" @mouseup="onMouseUp">你的浏览器不支持 canvas，请升级你的浏览器。</canvas>
    </div>
    <div>[{{ lastX + ', ' + lastY }}]</div>
    <div>
      <button @click="onReload">重写</button>
    </div>
    <div>返回相近字：{{ write_result }}</div>
  </div>
</template>

<script>
export default {
  name: 'App',
  data() {
    return {
      initX: 0, // 初始横坐标
      initY: 0, // 初始纵坐标
      lastX: 0, // 上一个横坐标
      lastY: 0, // 上一个纵坐标
      isHandWrite: false, // 是否开始手写
      pointsXY: [], // 单笔画
      allPointsXY: [], // 全部笔画
      write_result: [], // 返回相近字
    }
  },
  mounted() {
    this.initBound()

    let _this = this
    // 添加jsonp回调函数, qq输入法特定
    window['QQShuru'] = {
      HWPanel: {
        ajax_callback: function (res) {
          _this.write_result = res.cand
        },
      },
    }
  },
  methods: {
    // 初始化canvas位置
    initBound() {
      let bound = this.$refs.canvas.getBoundingClientRect()
      this.initX = bound.x
      this.initY = bound.y
    },
    onMouseDown(e) {
      console.log('onDown', e)
      this.pointsXY = []
      let cx = e.clientX - this.initX
      let cy = e.clientY - this.initY
      this.lastX = cx
      this.lastY = cy
      this.pointsXY.push(cx)
      this.pointsXY.push(cy)
      this.isHandWrite = true
    },
    onMouseMove(e) {
      if (this.isHandWrite) {
        let cx = e.clientX - this.initX
        let cy = e.clientY - this.initY
        this.pointsXY.push(cx - this.lastX)
        this.pointsXY.push(cy - this.lastY)
        // 获取2d上下文对象
        let ctx = this.$refs.canvas.getContext('2d')
        // 新建一条路径
        ctx.beginPath()
        ctx.strokeStyle = '#000'
        ctx.fillStyle = '#000'
        ctx.lineWidth = 8
        ctx.lineCap = 'round'
        ctx.moveTo(this.lastX, this.lastY)
        ctx.lineTo(cx, cy)
        ctx.stroke()
        this.lastX = cx
        this.lastY = cy
      }
    },
    onMouseUp(e) {
      if (this.isHandWrite) {
        this.isHandWrite = false
        this.allPointsXY.push(this.pointsXY.join(','))
        this.queryText()
      }
    },
    // 识别文字
    queryText() {
      let track_str = this.allPointsXY.join(',eb,')
      this.$jsonp(
        `https://handwriting.shuru.qq.com/cloud/cgi-bin/cloud_hw_pub.wsgi?track_str=${track_str}&cmd=0`
      ).catch(err => {
        console.log(err)
      })
    },
    onReload() {
      if (!this.$refs.canvas) return
      this.pointsXY = []
      this.allPointsXY = []
      let ctx = this.$refs.canvas.getContext('2d')
      ctx.clearRect(0, 0, 300, 200)
    },
  },
}
</script>

<style lang="scss">
#app {
  font-family: Avenir, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;

  .canvas-container {
    background: #fafafa;

    canvas {
      background: #fff;
      border: 1px solid #000;
    }
  }
}
</style>

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