https://developers.weixin.qq.com/miniprogram/dev/api/share/wx.showShareImageMenu.html#%E7%A4%BA%E4%BE%8B%E4%BB%A3%E7%A0%81

wx.downloadFile({
    url: 'https://res.wx.qq.com/wxdoc/dist/assets/img/demo.ef5c5bef.jpg',
    success: (res) => {
        console.log(res.tempFilePath);
        wx.showShareImageMenu({
            path: res.tempFilePath,
            success: (res) => {
                console.log('success', res)
            }, fail: (res) => {
                console.log('fail', res)
            }


        })
    }
})