I would like to suggest following the system default theme that is available from Android 10 (API level 29):
Issue with high resolution contact picture
When I select a picture from the gallery as contact picture it shows up at nice resolution in the adressbook. Now as soon as I sync davdroid with my remote Baikal server, picture becomes very low resolutions and heavily pixelized.
In order to find the source of the problem I also installed CardDAV-Sync free, created a new contact with a high-rez contact picture and synced it to my Baikal server. In that case photo stays at its original size. Now if I delete the CardDAV-Sync account, I can still see the recently added contact since its is on Baikal and davdroid uses the same addressbook. Now if I edit that particular contact and change the phone number for example, sync then the contact picture is converted to the low rez version.
I would also like to see the resolution of contact pictures stay untouched.
Contact photos are now read from the high-res photo file instead of the low-res thumbnail column.
However, when importing photos, they’re still written to the database thumbnail blob instead of creating an asset file. This might cause memory issues, but for the moment, it’s too complicated to import contacts and contact assets separately.
I’m having the same problem with davdroid 0.7.1 (from fdroid) and baikal 2.0.0 alpha.