微信小程序?qū)崿F(xiàn)圖片雙滑縮放大小

   Page({
  data: {
    touch: {
      distance: 0,
      scale: 1,
      baseWidth: null,
      baseHeight: null,
      scaleWidth: null,
      scaleHeight: null
    }
  },
  touchStartHandle(e) {
    // 單手指縮放開始，也不做任何處理 
    if (e.touches.length == 1) {
      console.log("單滑了")
      return
    }
    console.log('雙手指觸發(fā)開始')
    // 注意touchstartCallback 真正代碼的開始 
    // 一開始我并沒有這個(gè)回調(diào)函數(shù)，會(huì)出現(xiàn)縮小的時(shí)候有瞬間被放大過程的bug 
    // 當(dāng)兩根手指放上去的時(shí)候，就將distance 初始化。 
    let xMove = e.touches[1].clientX - e.touches[0].clientX;
    let yMove = e.touches[1].clientY - e.touches[0].clientY;
    let distance = Math.sqrt(xMove * xMove + yMove * yMove);
    this.setData({
      'touch.distance': distance,
    })
  },
  touchMoveHandle(e) {
    let touch = this.data.touch
    // 單手指縮放我們不做任何操作 
    if (e.touches.length == 1) {
      console.log("單滑了");
      return
    }
    console.log('雙手指運(yùn)動(dòng)開始')
    let xMove = e.touches[1].clientX - e.touches[0].clientX;
    let yMove = e.touches[1].clientY - e.touches[0].clientY;
    // 新的 ditance 
    let distance = Math.sqrt(xMove * xMove + yMove * yMove);
    let distanceDiff = distance - touch.distance;
    let newScale = touch.scale + 0.005 * distanceDiff
    // 為了防止縮放得太大，所以scale需要限制，同理最小值也是 
    if (newScale >= 2) {
      newScale = 2
    }
    if (newScale <= 0.6) {
      newScale = 0.6
    }
    let scaleWidth = newScale * touch.baseWidth
    let scaleHeight = newScale * touch.baseHeight
    // 賦值 新的 => 舊的 
    this.setData({
      'touch.distance': distance,
      'touch.scale': newScale,
      'touch.scaleWidth': scaleWidth,
      'touch.scaleHeight': scaleHeight,
      'touch.diff': distanceDiff
    })
  },
  load: function (e) {
    // bindload 這個(gè)api是<image>組件的api類似<img>的onload屬性 
    this.setData({
      'touch.baseWidth': e.detail.width,
      'touch.baseHeight': e.detail.height,
      'touch.scaleWidth': e.detail.width,
      'touch.scaleHeight': e.detail.height
    });
  }
})

<image mode='scaleToFill' src='../../../images/01.jpg' bindtouchstart='touchStartHandle' bindtouchmove='touchMoveHandle' bindload='load' style="width: {{ touch.scaleWidth }}px;height: {{ touch.scaleHeight }}px"></image>