How programaticaly convert png image in Resources directory in byte [] array (64)

I am developing one app in cross platform (iOS, Android and UWP) with xaml and c#. My database is SQLigth and the column type is Blob.
As I have an standard picture in png format (in Resources directory), I need programmatically convert them (without user intervention) in byte [] array (64) when the app start.
After the convertion I will save the array in the mentioned database column.
Please, help me with complete code if it is possible.
Thanks a lot (excuse my english).