Cesium Electron app cached imagery (GeoPackage)

I have created a Cesium app using electron. I am trying to support offline map imagery. I am currently taking a GeoPackage extracting it and converting it into a directory structure, which follows the Google Tiling scheme.

I am trying to use the UrlTemplateImageryProvider imagery provider to read the imagery out of the directory structure. Using a url like:

url : 'file:///C:/offlineImagery/{z}/{x}/{y}.jpeg'

I have tried using different tilingSchemes, ... but it seems like the x and y values being requested do not match the what I expect.

Anybody have any ideas?

Thanks in advance

Jerrold Stoy

Attached are two small clips, the first clip is a video showing what I am seeing on the screen which is a black box where the imagery should appear. The second clip shows that one of the imagery tiles was loaded successfully, but it never appeared on the globe.

Thanks in advance