小程序设置微信背景图片的时候，无法引用本地图片，所以需要转换喂base64的格式，

let aa =  'data:image/png;base64,' + wx.getFileSystemManager().readFileSync('../index/login-bg.png','base64');

    console.log(aa)

我的图片的路径是在index文件夹下的。

但是会报下面的错误

WAServiceMainContext.js:9 Error: readFileSync:fail permission denied, open ../index/login-bg.png

    at Di (WAServiceMainContext.js:9)

    at Object.r.<computed> (WAServiceMainContext.js:9)

    at Object.t.<computed> [as readFileSync] (WAServiceMainContext.js:9)

    at xo.onLoad (index.js? [sm]:4)

    at xo.<anonymous> (WASubContext.js?t=wechat&s=1656919390203&v=2.24.7:23)

    at xo.i.__callPageLifeTime__ (WASubContext.js?t=wechat&s=1656919390203&v=2.24.7:23)

    at WASubContext.js?t=wechat&s=1656919390203&v=2.24.7:23

    at WAServiceMainContext.js:9

    at WASubContext.js?t=wechat&s=1656919390203&v=2.24.7:23

    at WAServiceMainContext.js:9(env: Windows,mp,1.05.2204250; lib: 2.24.7)