The permission must be declared in the AndroidManifest.xml of the APK. This is where existing APKs need to be patched or compiled with the change. See
Then the app must be installed in /system/priv-app (or on the vendor partition). It must also be granted the system camera in /system/etc/permissions. For the stock camera we add privapp-permissions-com.fp.camera.xml
<?xml version="1.0" encoding="utf-8"?>
<permissions>
<privapp-permissions package="com.fp.camera">
<permission name="android.permission.SYSTEM_CAMERA"/>
</privapp-permissions>
</permissions>
And last the camera package name must also be whitelisted in vendor.camera.aux.packagelist property. It’s easier to disable that property so that it’s empty. Then all apps are allowed if they fulfill the other requirements …
Camera2 from AOSP shows 12MP in the settings, but the captured image is not. I didn’t try modify if for SYSTEM_CAMERA permission. Also don’t know if it supports aux cameras at all.
I believe 12MP is the intended native resolution of the sensor. The “high res” 48mp images are probably only available in a special capture mode. Afaik that is a function of the Qualcomm camera HAL but the camera Apps need special support for it.
Because it implements all the features like High Res, Timelapse, Slomo etc and it can be extracted from the stock images like the other blobs. Usability is easier than for OpenCamera. Also I think it’s probably the best baseline for custom ROMs to see what features are working and which are not.