Page({
 data: {
  touch: {
   distance: 0,
   scale: 1,
   baseWidth: null,
   baseHeight: null,
   scaleWidth: null,
   scaleHeight: null
  }
 },
 touchStartHandle(e) {
 // 单手指缩放开始，也不做任何处理
 if (e.touches.length == 1) {
   console.log("单滑了")
 return
  }
  console.log('双手指触发开始')
 // 注意touchstartCallback 真正代码的开始
  // 一开始我并没有这个回调函数，会出现缩小的时候有瞬间被放大过程的bug
  // 当两根手指放上去的时候，就将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
 // 单手指缩放我们不做任何操作
 if (e.touches.length == 1) {
   console.log("单滑了");
 return
  }
  console.log('双手指运动开始')
  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
 // 为了防止缩放得太大，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
 // 赋值 新的 => 旧的
 this.setData({
 'touch.distance': distance,
 'touch.scale': newScale,
 'touch.scaleWidth': scaleWidth,
 'touch.scaleHeight': scaleHeight,
 'touch.diff': distanceDiff
  })
 },
 load: function (e) {
 // bindload 这个api是<image>组件的api类似<img>的onload属性
 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>