const canvasBoxEl = document.getElementById(\'canvas-box\')
this.boxWidth = canvasBoxEl.width
this.boxHeight = canvasBoxEl.height
console.log(canvasBoxEl)
var url = \'./static/react-native.pdf\'
PDFJS.getDocument(url)
  .promise.then(pdf => {
    // pdf.numPages 总页数
    return pdf.getPage(1)
  })
  .then(page => {
    // 设置展示比例
    var scale = 1.5
    // 获取pdf尺寸
    var viewport = page.getViewport({ scale })
    console.log(viewport)
    // 获取需要渲染的元素
    var canvas = document.createElement(\'canvas\')
    var context = canvas.getContext(\'2d\')
    canvas.height = viewport.height
    canvas.width = viewport.width
    canvasBoxEl.appendChild(canvas)
    var renderContext = {
      canvasContext: context,
      viewport: viewport
    }

    page.render(renderContext)
  })

const CSS_UNITS = 96.0 / 72.0;
// const PRINT_UNITS = 150 / 72.0;

let userAgent = (typeof navigator !== "undefined" && navigator.userAgent) || "";
let platform = (typeof navigator !== "undefined" && navigator.platform) || "";
let maxTouchPoints =
  (typeof navigator !== "undefined" && navigator.maxTouchPoints) || 1;

let maxCanvasPixels = 16777216;

let isAndroid = /Android/.test(userAgent);
let isIOS =
  /\b(iPad|iPhone|iPod)(?=;)/.test(userAgent) ||
  (platform === "MacIntel" && maxTouchPoints > 1);
(function checkCanvasSizeLimitation() {
  if (isIOS || isAndroid) {
    maxCanvasPixels = 5242880;
  }
})();

function approximateFraction(x) {
  if (Math.floor(x) === x) {
    return [x, 1];
  }

  var xinv = 1 / x;
  var limit = 8;

  if (xinv > limit) {
    return [1, limit];
  } else if (Math.floor(xinv) === xinv) {
    return [1, xinv];
  }

  var x_ = x > 1 ? xinv : x;
  var a = 0,
    b = 1,
    c = 1,
    d = 1;

  while (q < limit) {
    var p = a + c,
      q = b + d;

    if (q > limit) {
      break;
    }

    if (x_ <= p / q) {
      c = p;
      d = q;
    } else {
      a = p;
      b = q;
    }
  }

  var result;

  if (x_ - a / b < c / d - x_) {
    result = x_ === x ? [a, b] : [b, a];
  } else {
    result = x_ === x ? [c, d] : [d, c];
  }

  return result;
},
function roundToDivide(x, div) {
  var r = x % div;
  return r === 0 ? x : Math.round(x - r + div);
}

let devicePixelRatio = window.devicePixelRatio || 1
      let backingStoreRatio =
        ctx.webkitBackingStorePixelRatio ||
        ctx.mozBackingStorePixelRatio ||
        ctx.msBackingStorePixelRatio ||
        ctx.oBackingStorePixelRatio ||
        ctx.backingStorePixelRatio ||
        1
 const pixelRatio = devicePixelRatio / backingStoreRatio

<template>
  <div class="pdf-touch-box">
    <div class="scale-btn-box" :style="{ width: btnWidth + \'px\' }">
      <button class="scale-btn" @click="scaleCanvas(1.5)">1.5</button>
      <button class="scale-btn" @click="scaleCanvas(0.5)">0.5</button>
      <button class="scale-btn" @click="scaleCanvas(1)">还原(1)</button>
    </div>

    <div v-show="!loading" class="pdf-canvas-wrap" :style="{ width: viewWidth + \'px\', height: viewHeight + \'px\' }"></div>
    <p class="pdf-canvas-tips" v-show="loading">正在加载...</p>
  </div>
</template>

<script>
import * as PDFJS from \'pdfjs-dist\'

// 本地
// window.pdfjsWorker = require("pdfjs-dist/build/pdf.worker.js");

// cdn 2.8.335  2.6.347 2.5.207
PDFJS.GlobalWorkerOptions.workerSrc = \'https://cdn.jsdelivr.net/npm/pdfjs-dist@2.6.347/build/pdf.worker.min.js\'

// https://github.com/mozilla/pdf.js/blob/master/examples/node/getinfo.js
// Requires single file built version of PDF.js -- please run
// `gulp singlefile` before running the example.
// const pdfjsLib = require("pdfjs-dist/legacy/build/pdf.js");

const CSS_UNITS = 96.0 / 72.0
// const PRINT_UNITS = 150 / 72.0;

let userAgent = (typeof navigator !== \'undefined\' && navigator.userAgent) || \'\'
let platform = (typeof navigator !== \'undefined\' && navigator.platform) || \'\'
let maxTouchPoints = (typeof navigator !== \'undefined\' && navigator.maxTouchPoints) || 1

let maxCanvasPixels = 16777216
// PDF之外占据的宽度 -18 padding -18减去滚动条宽度（不确定）
let autoWidth = 36

let isAndroid = /Android/.test(userAgent)
let isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(userAgent) || (platform === \'MacIntel\' && maxTouchPoints > 1)
;(function checkCanvasSizeLimitation() {
  if (isIOS || isAndroid) {
    maxCanvasPixels = 5242880
    autoWidth -= 18
  }
})()

export default {
  data() {
    return {
      src: \'./static/react-native.pdf\',
      loading: true,
      pdfDoc: null,
      boxEl: null,
      wrapEl: null,
      areaWidth: 0,
      btnWidth: 0,
      viewWidth: 0,
      viewHeight: 0,
      pixelRatio: 2,
      isFirstTimeRender: true,
      viewport: null,
      canvasEles: [],
      canvasCtxs: [],
      totallPage: 1,
      pageScale: 1, // pdf 适应窗口产生的 scale
      curCanvasCSSWh: null,
      transform: null,
      pageRendered: false
    }
  },
  mounted() {
    this.init()
  },
  methods: {
    async init() {
      this.boxEl = document.querySelector(\'.pdf-touch-box\')
      this.wrapEl = document.getElementsByClassName(\'pdf-canvas-wrap\')[0]
      this.btnWidth = this.areaWidth = this.boxEl.clientWidth

      const loadingState = await this.getPDF()
      if (loadingState === \'success\') this.initRenderOneByOne()
      else this.boxEl.innerText = loadingState
    },
    scaleCanvas(scale) {
      if (!this.pageRendered) return

      // 改变 viewport 大小
      this.viewport = this.viewport.clone({
        scale: this.pageScale * scale * CSS_UNITS
      })
      const { styleWidth, styleHeight } = this.getCanvasCSSWH()
      // 先改变CSS canvas 会变模糊
      this.canvasEles.forEach((canvas, index) => {
        // 不修改 width height 不然会重置 canvas
        canvas.style.width = styleWidth + \'px\'
        canvas.style.height = styleHeight + \'px\'
        console.log(index)
      })
      // 重新渲染 变清晰
      this.scaleRenderAll()
    },
    // 好像改变也不是很明显
    // scaleCanvas(scale) {
    //   // 改变 viewport 大小
    //   this.viewport = this.viewport.clone({
    //     scale: this.pageScale * scale * CSS_UNITS,
    //   });
    //   // 逐个重新渲染
    //   this.renderSinglePage(this.canvasEles[0], 1);
    // },

    getPDF() {
      let that = this
      return new Promise(reslove => {
        PDFJS.getDocument(that.src).promise.then(
          function (pdfDoc_) {
            that.pdfDoc = pdfDoc_
            that.totallPage = pdfDoc_.numPages
            that.loading = false
            reslove(\'success\')
          },
          function (reason) {
            console.log(reason.message)
            that.loading = false
            reslove(reason.name)
          }
        )
      })
    },

    initRenderOneByOne() {
      for (let pageNum = 1; pageNum <= this.totallPage; pageNum++) {
        let canvas = document.createElement(\'canvas\')
        canvas.setAttribute(\'id\', `pdf-canvas${pageNum}`)
        canvas.setAttribute(\'class\', `pdfcanvas`)
        // alpha 设定 canvas 背景总是不透明，可以加快浏览器绘制透明的内容和图片 初始化出来 canvas 为黑色背景
        // 实际上 导致 重新渲染的时候 闪黑屏
        // let ctx = canvas.getContext("2d", {
        //   alpha: false,
        // });
        let ctx = canvas.getContext(\'2d\')
        this.canvasCtxs.push(ctx)
        this.canvasEles.push(canvas)
        this.wrapEl.appendChild(canvas)
      }
      this.renderSinglePage(this.canvasEles[0], 1)
    },

    renderSinglePage(canvas, pageNum) {
      let ctx = this.canvasCtxs[pageNum - 1]
      let that = this

      this.pdfDoc.getPage(pageNum).then(function (page) {
        if (that.isFirstTimeRender) that.initView(page, ctx)

        if (pageNum === 1) that.getCanvasCSSWH()

        canvas.width = that.curCanvasCSSWh.width
        canvas.height = that.curCanvasCSSWh.height
        canvas.style.width = that.curCanvasCSSWh.styleWidth + \'px\'
        canvas.style.height = that.curCanvasCSSWh.styleHeight + \'px\'
        canvas.style[\'border\'] = \'#d6d6d6 solid 1px\'
        canvas.style.margin = \'9px 0 0 0\'

        let renderContext = {
          canvasContext: ctx,
          transform: that.transform,
          viewport: that.viewport,
          enableWebGL: false,
          renderInteractiveForms: false
        }
        let renderTask = page.render(renderContext)

        renderTask.promise.then(function () {
          if (that.totallPage >= ++pageNum) {
            that.renderSinglePage(that.canvasEles[pageNum - 1], pageNum)
          } else {
            that.pageRendered = true
          }
        })
      })
    },

    scaleRenderAll() {
      const len = this.canvasEles.length
      for (let pageNum = 0; pageNum < len; pageNum++) {
        let canvas = this.canvasEles[pageNum]
        let ctx = this.canvasCtxs[pageNum]

        let that = this
        this.pdfDoc.getPage(pageNum + 1).then(function (page) {
          canvas.width = that.curCanvasCSSWh.width
          canvas.height = that.curCanvasCSSWh.height

          let renderContext = {
            canvasContext: ctx,
            transform: that.transform,
            viewport: that.viewport,
            enableWebGL: false,
            renderInteractiveForms: false
          }
          let renderTask = page.render(renderContext)

          renderTask.promise.then(function (context) {
            console.log(context)
          })
        })
      }
    },

    getCanvasCSSWH() {
      let outputScale = {
        sx: this.pixelRatio,
        sy: this.pixelRatio,
        scaled: this.pixelRatio !== 1
      }

      let pixelsInViewport = this.viewport.width * this.viewport.height
      let maxScale = Math.sqrt(maxCanvasPixels / pixelsInViewport)

      if (outputScale.sx > maxScale || outputScale.sy > maxScale) {
        outputScale.sx = maxScale
        outputScale.sy = maxScale
        outputScale.scaled = true
      }

      let sfx = (0, this.approximateFraction)(outputScale.sx)
      let sfy = (0, this.approximateFraction)(outputScale.sy)
      const width = (0, this.roundToDivide)(this.viewport.width * outputScale.sx, sfx[0])
      const height = (0, this.roundToDivide)(this.viewport.height * outputScale.sy, sfy[0])
      const styleWidth = (0, this.roundToDivide)(this.viewport.width, sfx[1])
      const styleHeight = (0, this.roundToDivide)(this.viewport.height, sfy[1])

      if (this.pixelRatio !== 1) this.transform = [this.pixelRatio, 0, 0, this.pixelRatio, 0, 0]

      this.viewWidth = styleWidth + 2
      // 12 加上 canvas border margin 误差？2 + 9 + 1
      this.viewHeight = this.totallPage * (this.viewport.height + 12) + 9

      this.curCanvasCSSWh = { width, height, styleWidth, styleHeight }
      return this.curCanvasCSSWh
    },
    approximateFraction(x) {
      if (Math.floor(x) === x) {
        return [x, 1]
      }

      var xinv = 1 / x
      var limit = 8

      if (xinv > limit) {
        return [1, limit]
      } else if (Math.floor(xinv) === xinv) {
        return [1, xinv]
      }

      var x_ = x > 1 ? xinv : x
      var a = 0,
        b = 1,
        c = 1,
        d = 1

      while (q < limit) {
        var p = a + c,
          q = b + d

        if (q > limit) {
          break
        }

        if (x_ <= p / q) {
          c = p
          d = q
        } else {
          a = p
          b = q
        }
      }

      var result

      if (x_ - a / b < c / d - x_) {
        result = x_ === x ? [a, b] : [b, a]
      } else {
        result = x_ === x ? [c, d] : [d, c]
      }

      return result
    },
    roundToDivide(x, div) {
      var r = x % div
      return r === 0 ? x : Math.round(x - r + div)
    },

    initView(page, ctx) {
      let devicePixelRatio = window.devicePixelRatio || 1
      let backingStoreRatio =
        ctx.webkitBackingStorePixelRatio ||
        ctx.mozBackingStorePixelRatio ||
        ctx.msBackingStorePixelRatio ||
        ctx.oBackingStorePixelRatio ||
        ctx.backingStorePixelRatio ||
        1
      this.pixelRatio = devicePixelRatio / backingStoreRatio

      this.viewport = page.getViewport({
        scale: CSS_UNITS
      })
      console.log(this.viewport)

      this.pageScale = (this.areaWidth - autoWidth) / this.viewport.width
      let curViewport = page.getViewport({
        scale: this.pageScale * CSS_UNITS
      })
      this.viewport = curViewport

      this.isFirstTimeRender = false
    },

    drawBorder(canvas, ctx) {
      ctx.save()
      ctx.fillStyle = \'rgb(255, 255, 255)\'
      ctx.strokeRect(0, 0, canvas.width, canvas.height)
      ctx.restore()
    }
  }
}
</script>

<style scoped>
.pdf-touch-box {
  padding: 9px;
  width: calc(100% - 18px);
  height: calc(100% - 18px);
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.scale-btn-box {
  position: fixed;
  top: 0;
  left: 0;
  height: 44px;
  display: flex;
  justify-content: space-around;
}
.scale-btn {
  width: 25%;
  height: 100%;
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  background: #fff;
  border: 1px solid #dcdfe6;
  color: #606266;
  -webkit-appearance: none;
  text-align: center;
  box-sizing: border-box;
  outline: none;
  margin: 0;
  transition: 0.1s;
  font-weight: 500;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  padding: 12px 20px;
  font-size: 14px;
  border-radius: 4px;
}
.pdf-canvas-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  overflow: hidden;
  margin-top: 44px;
  padding-top: 9px;
}
.pdf-canvas-tips {
  margin-top: 44px;
}
</style>

import AlloyFinger from "alloyfinger";
//包装一下 不然 eslint 报警告
class FingerTouch {
  constructor(element, options) {
    Object.assign(this, AlloyFinger.prototype);
    AlloyFinger.call(this, element, options);
  }
}

this.alloyFinger = new FingerTouch(this.wrapEl, {})
this.alloyFinger.on(\'pinch\', e => {
  let zoom = e.zoom
  let curScale = this.lastStyleScale * zoom
  if (curScale <= this.pageScale / 2 || curScale >= 5) return
  this.scaleEvent(curScale)
})

this.alloyFinger.on(\'pressMove\', e => {
  this.viewTop += e.deltaY
  this.viewLeft += e.deltaX
})

<template>
  <div class="pdf-touch-box">
    <div class="scale-btn-box" :style="{ width: btnWidth + \'px\' }">
      <button class="scale-btn" @click="scaleEvent(3.5)">3.5</button>
      <button class="scale-btn" @click="scaleEvent(2.5)">2.5</button>
      <button class="scale-btn" @click="scaleEvent(1.8)">1.8</button>
      <button class="scale-btn" @click="scaleEvent(1.3)">1.3</button>
      <button class="scale-btn" @click="scaleEvent(1)">1</button>
      <button class="scale-btn" @click="scaleEvent(0.5)">0.5</button>
    </div>

    <div
      v-show="!loading"
      class="pdf-canvas-wrap"
      :style="{
        top: viewTop + \'px\',
        left: viewLeft + \'px\',
        width: viewWidth + \'px\',
        height: viewHeight + \'px\'
      }"
    ></div>
    <p class="pdf-canvas-tips" v-show="loading">正在加载...</p>
  </div>
</template>

<script>
import * as PDFJS from \'pdfjs-dist\'
console.log(PDFJS)

import { TextLayerBuilder, EventBus } from \'pdfjs-dist/web/pdf_viewer\'
import \'pdfjs-dist/web/pdf_viewer.css\'
console.log(TextLayerBuilder)

// 本地
// window.pdfjsWorker = require("pdfjs-dist/build/pdf.worker.js");

// cdn 2.8.335  2.6.347 2.5.207
PDFJS.GlobalWorkerOptions.workerSrc = \'https://cdn.jsdelivr.net/npm/pdfjs-dist@2.6.347/build/pdf.worker.min.js\'

// https://github.com/mozilla/pdf.js/blob/master/examples/node/getinfo.js
// Requires single file built version of PDF.js -- please run
// `gulp singlefile` before running the example.
// const pdfjsLib = require("pdfjs-dist/legacy/build/pdf.js");

const CSS_UNITS = 96.0 / 72.0
// const PRINT_UNITS = 150 / 72.0;

let userAgent = (typeof navigator !== \'undefined\' && navigator.userAgent) || \'\'
let platform = (typeof navigator !== \'undefined\' && navigator.platform) || \'\'
let maxTouchPoints = (typeof navigator !== \'undefined\' && navigator.maxTouchPoints) || 1

let maxCanvasPixels = 16777216
// PDF之外占据的宽度 -18 padding -18减去滚动条宽度（不确定）
let autoWidth = 36
let textLayerTop = 3
let scaleInterval = 0.05

let isAndroid = /Android/.test(userAgent)
let isIOS = /\b(iPad|iPhone|iPod)(?=;)/.test(userAgent) || (platform === \'MacIntel\' && maxTouchPoints > 1)
;(function checkCanvasSizeLimitation() {
  if (isIOS || isAndroid) {
    maxCanvasPixels = 5242880
    autoWidth -= 18
    textLayerTop -= 1
    // 手机上面缩放对清晰度影响更小
    scaleInterval = 0.4
  }
})()
import AlloyFinger from \'alloyfinger\'
//包装一下 不然 eslint 报警告
class FingerTouch {
  constructor(element, options) {
    Object.assign(this, AlloyFinger.prototype)
    AlloyFinger.call(this, element, options)
  }
}

export default {
  data() {
    return {
      src: \'./static/react-native.pdf\',
      loading: true,
      pdfDoc: null,
      boxEl: null,
      wrapEl: null,
      areaWidth: 0,
      btnWidth: 0,
      viewWidth: 0,
      viewHeight: 0,
      pixelRatio: 2,
      isFirstTimeRender: true,
      viewport: null,
      canvasEles: [],
      canvasCtxs: [],
      totallPage: 0,
      pageScale: 1, // pdf 适应窗口产生的 scale
      curCanvasCSSWh: null,
      transform: null,
      pageRenderedNum: 0,
      scaleTimer: null,
      lastStyleScale: 1,
      lastRerenderScale: 1,
      alloyFinger: null,
      viewTop: 0,
      viewLeft: 9,
      textEls: []
    }
  },
  mounted() {
    this.init()
  },
  methods: {
    async init() {
      //禁止下拉刷新
      document.addEventListener(
        \'touchmove\',
        function (ev) {
          ev.preventDefault()
        },
        { passive: false }
      )
      this.boxEl = document.querySelector(\'.pdf-touch-box\')
      this.wrapEl = document.getElementsByClassName(\'pdf-canvas-wrap\')[0]
      this.btnWidth = this.areaWidth = this.boxEl.clientWidth

      const loadingState = await this.getPDF()
      if (loadingState === \'success\') {
        this.initRenderOneByOne()
        this.initTouch()
      } else this.boxEl.innerText = loadingState
    },
    initTouch() {
      this.alloyFinger = new FingerTouch(this.wrapEl, {})
      this.alloyFinger.on(\'pinch\', e => {
        let zoom = e.zoom
        let curScale = this.lastStyleScale * zoom
        if (curScale <= this.pageScale / 2 || curScale >= 5) return
        this.scaleEvent(curScale)
      })

      this.alloyFinger.on(\'pressMove\', e => {
        this.viewTop += e.deltaY
        this.viewLeft += e.deltaX
      })
    },
    scaleEvent(scale) {
      // 渲染中 不让缩放 也不让重绘
      if (this.pageRenderedNum != this.totallPage || this.totallPage === 0) return

      // 没在渲染中 随意缩放
      this.scaleCanvas(scale)

      // 说明是第一次事件 或重绘完成 开始计时
      if (this.scaleTimer === null) {
        this.scaleTimer = this.renderDelayer(666)
      }
      //时间间隔内再次触发缩放 重新计时
      clearTimeout(this.scaleTimer)
      this.scaleTimer = this.renderDelayer(666)
    },
    renderDelayer(interval) {
      return setTimeout(() => {
        this.scaleRenderAll()
        this.scaleTimer = null
      }, interval)
    },
    scaleTopLeft(width, height) {
      if (Math.abs(this.viewTop) > height / 2) this.viewTop *= 1 / 2
      if (Math.abs(this.viewLeft) > width / 2) this.viewLeft *= 1 / 2
    },
    scaleCanvas(scale) {
      this.lastStyleScale = scale
      console.log(scale)
      // 改变 viewport 大小
      this.viewport = this.viewport.clone({
        scale: (this.pageScale * CSS_UNITS * scale).toFixed(3)
      })

      const { styleWidth, styleHeight } = this.getCanvasCSSWH()

      // 计算一下 top left 不然可能会显示到 窗口外面 看不到了
      this.scaleTopLeft(styleWidth, styleHeight)

      // 改变CSS canvas 会变模糊
      this.canvasEles.forEach(canvas => {
        // 不修改 width height 不然会重置 canvas 变空白
        canvas.style.width = styleWidth + \'px\'
        canvas.style.height = styleHeight + \'px\'
      })
    },
    // 使用新渲染的 canvas  替换 缩放过后不清晰的 canvas
    scaleRenderAll() {
      let curInterval = Math.abs(this.lastStyleScale - this.lastRerenderScale)
      let curScaleInterval = scaleInterval
      let isNarrow = this.lastStyleScale < this.lastRerenderScale
      // 如果是变小 变化不大时 清晰度影响更小
      if (isNarrow) curScaleInterval = scaleInterval * 2

      console.log(\'scaleRenderAll\', curScaleInterval, curInterval)
      // 变化很小的时候就不计时重新渲染了 清晰度影响不大 1.1 - 1 = 0.10000000000000009
      if (curInterval <= curScaleInterval) return

      this.lastRerenderScale = this.lastStyleScale

      this.pageRenderedNum = 0
      const len = this.canvasEles.length
      for (let pageNum = 1; pageNum <= len; pageNum++) {
        let newCanvas = document.createElement(\'canvas\')
        let newCtx = newCanvas.getContext(\'2d\', {
          alpha: false
        })
        newCanvas.setAttribute(\'id\', `pdf-canvas${pageNum}`)

        this.canvasCtxs[pageNum - 1] = newCtx

        let that = this
        this.pdfDoc.getPage(pageNum).then(function (page) {
          that.setCanvasCSSWh.call(that, newCanvas)

          let renderTask = that.pageRender.call(that, page, newCtx)

          renderTask.promise
            .then(function () {
              let oldCanvas = that.canvasEles[pageNum - 1]
              oldCanvas.parentElement.replaceChild(newCanvas, oldCanvas)
              that.canvasEles[pageNum - 1] = newCanvas
              that.pageRenderedNum++

              return page.getTextContent()
            })
            .then(textContent => that.textRerender.call(that, pageNum, textContent))
            .catch(e => console.log(e))
        })
      }
    },

    getPDF() {
      let that = this
      return new Promise(reslove => {
        PDFJS.getDocument(that.src).promise.then(
          function (pdfDoc_) {
            that.pdfDoc = pdfDoc_
            that.totallPage = 1
            // that.totallPage = pdfDoc_.numPages;
            that.loading = false
            reslove(\'success\')
          },
          function (reason) {
            console.log(reason.message)
            that.loading = false
            reslove(reason.name)
          }
        )
      })
    },

    initRenderOneByOne() {
      for (let pageNum = 1; pageNum <= this.totallPage; pageNum++) {
        let canvas = document.createElement(\'canvas\')
        canvas.setAttribute(\'id\', `pdf-canvas${pageNum}`)
        canvas.setAttribute(\'class\', `pdfcanvas`)
        // alpha 设定 canvas 背景总是不透明，可以加快浏览器绘制透明的内容和图片 初始化出来 canvas 为黑色背景
        // 实际上 导致 重新渲染的时候 闪黑屏
        // let ctx = canvas.getContext("2d", {
        //   alpha: false,
        // });
        let ctx = canvas.getContext(\'2d\')
        this.canvasCtxs.push(ctx)
        this.canvasEles.push(canvas)
        //  this.wrapEl.appendChild(canvas);

        let pageDiv = document.createElement(\'div\')
        pageDiv.setAttribute(\'id\', \'page-\' + pageNum)
        pageDiv.setAttribute(\'style\', \'position: relative;\')
        this.wrapEl.appendChild(pageDiv)
        pageDiv.appendChild(canvas)
      }
      this.renderSinglePage(this.canvasEles[0], 1)
    },

    renderSinglePage(canvas, pageNum) {
      let ctx = this.canvasCtxs[pageNum - 1]
      let that = this

      this.pdfDoc.getPage(pageNum).then(function (page) {
        if (that.isFirstTimeRender) that.initView(page, ctx)

        if (pageNum === 1) that.getCanvasCSSWH()

        that.setCanvasCSSWh.call(that, canvas)
        let renderTask = that.pageRender.call(that, page, ctx)

        renderTask.promise
          .then(function () {
            if (that.totallPage > pageNum) {
              that.renderSinglePage(that.canvasEles[pageNum], pageNum + 1)
            }
            that.pageRenderedNum++
            return page.getTextContent()
          })
          .then(textContent => that.textRender.call(that, canvas, pageNum, textContent))
      })
    },
    textRerender(pageIndex, textContent) {
      const oldDiv = this.textEls[pageIndex - 1]

      const newDiv = document.createElement(\'div\')
      newDiv.setAttribute(\'class\', \'textLayer\')
      newDiv.setAttribute(\'style\', `top: ${textLayerTop}px`)

      oldDiv.parentElement.replaceChild(newDiv, oldDiv)
      this.textEls[pageIndex - 1] = newDiv
      this.renderTextLayer(newDiv, pageIndex, textContent)
    },
    textRender(canvas, pageIndex, textContent) {
      const textLayerDiv = document.createElement(\'div\')
      textLayerDiv.setAttribute(\'class\', \'textLayer\')
      textLayerDiv.setAttribute(\'style\', `top: ${textLayerTop}px`)
      canvas.parentElement.appendChild(textLayerDiv)
      this.textEls[pageIndex - 1] = textLayerDiv
      this.renderTextLayer(textLayerDiv, pageIndex, textContent)
    },
    renderTextLayer(el, index, content) {
      var textLayer = new TextLayerBuilder({
        eventBus: new EventBus(),
        textLayerDiv: el,
        pageIndex: index,
        viewport: this.viewport
      })

      textLayer.setTextContent(content)
      textLayer.render()
    },
    setCanvasCSSWh(canvas) {
      canvas.width = this.curCanvasCSSWh.width
      canvas.height = this.curCanvasCSSWh.height
      canvas.style.width = this.curCanvasCSSWh.styleWidth + \'px\'
      canvas.style.height = this.curCanvasCSSWh.styleHeight + \'px\'
      canvas.style[\'border\'] = \'#d6d6d6 solid 1px\'
      canvas.style.margin = \'0 0 9px 0\'
    },
    pageRender(page, ctx) {
      return page.render({
        canvasContext: ctx,
        transform: this.transform,
        viewport: this.viewport,
        enableWebGL: false,
        renderInteractiveForms: false
      })
    },

    drawBorder(canvas, ctx) {
      ctx.save()
      ctx.fillStyle = \'rgb(255, 255, 255)\'
      ctx.strokeRect(0, 0, canvas.width, canvas.height)
      ctx.restore()
    },
    getCanvasCSSWH() {
      let outputScale = {
        sx: this.pixelRatio,
        sy: this.pixelRatio,
        scaled: this.pixelRatio !== 1
      }

      let pixelsInViewport = this.viewport.width * this.viewport.height
      let maxScale = Math.sqrt(maxCanvasPixels / pixelsInViewport)

      if (outputScale.sx > maxScale || outputScale.sy > maxScale) {
        // 这里触发会出错
        // outputScale.sx = maxScale;
        // outputScale.sy = maxScale;
        // outputScale.scaled = true;
      }

      let sfx = (0, this.approximateFraction)(outputScale.sx)
      let sfy = (0, this.approximateFraction)(outputScale.sy)
      const width = (0, this.roundToDivide)(this.viewport.width * outputScale.sx, sfx[0])
      const height = (0, this.roundToDivide)(this.viewport.height * outputScale.sy, sfy[0])
      const styleWidth = (0, this.roundToDivide)(this.viewport.width, sfx[1])
      const styleHeight = (0, this.roundToDivide)(this.viewport.height, sfy[1])

      if (this.pixelRatio !== 1) this.transform = [this.pixelRatio, 0, 0, this.pixelRatio, 0, 0]

      this.viewWidth = styleWidth + 2
      // 12 加上 canvas border margin 误差？2 + 9 + 1
      this.viewHeight = this.totallPage * (this.viewport.height + 12) + 9

      this.curCanvasCSSWh = { width, height, styleWidth, styleHeight }
      return this.curCanvasCSSWh
    },
    approximateFraction(x) {
      if (Math.floor(x) === x) {
        return [x, 1]
      }

      var xinv = 1 / x
      var limit = 8

      if (xinv > limit) {
        return [1, limit]
      } else if (Math.floor(xinv) === xinv) {
        return [1, xinv]
      }

      var x_ = x > 1 ? xinv : x
      var a = 0,
        b = 1,
        c = 1,
        d = 1
      // eslint-disable-next-line
      while (true) {
        var p = a + c,
          q = b + d

        if (q > limit) {
          break
        }

        if (x_ <= p / q) {
          c = p
          d = q
        } else {
          a = p
          b = q
        }
      }

      var result

      if (x_ - a / b < c / d - x_) {
        result = x_ === x ? [a, b] : [b, a]
      } else {
        result = x_ === x ? [c, d] : [d, c]
      }

      return result
    },
    roundToDivide(x, div) {
      var r = x % div
      return r === 0 ? x : Math.round(x - r + div)
    },

    initView(page, ctx) {
      let devicePixelRatio = window.devicePixelRatio || 1
      let backingStoreRatio =
        ctx.webkitBackingStorePixelRatio ||
        ctx.mozBackingStorePixelRatio ||
        ctx.msBackingStorePixelRatio ||
        ctx.oBackingStorePixelRatio ||
        ctx.backingStorePixelRatio ||
        1
      this.pixelRatio = devicePixelRatio / backingStoreRatio

      this.viewport = page.getViewport({
        scale: CSS_UNITS
      })

      this.pageScale = (this.areaWidth - autoWidth) / this.viewport.width
      let curViewport = page.getViewport({
        scale: this.pageScale * CSS_UNITS
      })
      this.viewport = curViewport

      this.isFirstTimeRender = false
    }
  }
}
</script>

<style scoped>
.pdf-touch-box {
  padding: 9px;
  width: calc(100% - 18px);
  height: calc(100% - 18px);
  position: relative;
}
.scale-btn-box {
  position: fixed;
  top: 0;
  left: 0;
  height: 44px;
  display: flex;
  justify-content: space-around;
  z-index: 99;
}
.scale-btn-box::after {
  content: \'\';
  width: 100%;
  height: 100%;
  position: absolute;
  background: #fff;
  top: 0;
  left: 0;
  filter: blur(18px);
  opacity: 0.8;
}
.scale-btn {
  position: relative;
  z-index: 2;
  width: 25%;
  height: 100%;
  display: inline-block;
  line-height: 1;
  white-space: nowrap;
  cursor: pointer;
  background: #fff;
  border: 1px solid #dcdfe6;
  color: #606266;
  -webkit-appearance: none;
  text-align: center;
  box-sizing: border-box;
  outline: none;
  margin: 0;
  transition: 0.1s;
  font-weight: 500;
  -moz-user-select: none;
  -webkit-user-select: none;
  -ms-user-select: none;
  padding: 12px 20px;
  font-size: 14px;
  border-radius: 4px;
}
.pdf-canvas-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  overflow: hidden;
  margin-top: 44px;
  padding-top: 9px;
  position: absolute;
}
.pdf-canvas-tips {
  margin-top: 44px;
}
</style>