<?php
namespace app\home\controller;
use think\Controller;
class Upload extends First
{
  //上傳圖片API
  public function upImg() {
  	$arr = array('state'=>0,'msg'=>'上傳失敗','filepath'=>'');
    $file = request()->file('file');
    if($file){
      $info = $file->move('upload/weixin/');
      if ($info) {
        $arr['state'] = 1;
        $arr['msg'] = '上傳成功';
        $arr['filepath'] = $info->getSaveName();
      }
    }
    return json($arr);
  }
}

<image src='{{imgpath}}' style='width:600rpx; height:600rpx' />
<view>
 <button bindtap="upImg">點擊選擇上傳圖</button>
</view>

Page({
 data: {
  imgpath: ''
 },
 upImg: function (e) {
  var that = this
  wx.chooseImage({
   count: 1, // 默認最多一次上傳9張圖片
   sizeType: ['original', 'compressed'], // 允許原圖和壓縮圖
   sourceType: ['album', 'camera'], // 允許相冊和相機
   success(res) {
    const tempFilePaths = res.tempFilePaths
    wx.showToast({
     title: '正在上傳...',
     icon: 'loading',
     mask: true,
     duration: 500
    })
    wx.uploadFile({
     url: 'https://www.msllws.top/Upload/upImg', //服務器上傳接口
     filePath: tempFilePaths[0], //文件資源路徑
     name: 'file',
     header: {
      'Content-Type': 'Application/json'
     },
     success(res) {
      console.log(res)
      if (res.statusCode == 200){
       that.setData({
        imgpath: tempFilePaths
       }) 
      }
     }
    })
   }
  })
 }
})

<image src='{{imgpath}}' style='width:600rpx; height:600rpx' />
<view>
 <button bindtap="download">點擊下載</button>
</view>

Page({
 data: {
  imgpath: ''
 },
 download: function (e) {
  var that = this
  wx.showToast({
   title: '正在下載...',
   icon: 'loading',
   mask: true,
   duration: 500
  })
  wx.downloadFile({
   url: 'https://www.msllws.top/upload/1.jpg', //下載地址 
   type: 'image', //下載的資源類型（imnage/audio/video）
   success: function (res) {
    console.log(res)
    if (res.statusCode == 200) {
     var filepath = res.tempFilePath
     that.setData({
      imgpath: filepath
     })
    }
   }
  })
 }
})