<button bindtap="onChooseImage">选择图片</button>
<image class="img" src="{{chooseImageUrl}}" mode="widthFix"/>

// pages/02_common_cpns/index.js
Page({
  data: {
    message: "你好啊, 李银河!",
    chooseImageUrl: "",
    viewColors: ["red", "blue", "green", "skyblue", "purple", "yellow"]
  },
  
  onChooseImage() {
    wx.chooseMedia({
      mediaType: "image"
    }).then(res => {
      const imagePath = res.tempFiles[0].tempFilePath
      this.setData({ chooseImageUrl: imagePath })
    })
  },