I want to programmatically create a contact with an image with the result that when the iPhone receives a call from the number associated with that contact its image will appear on the incoming call screen (occupying the full screen, not the little tiny icon variation).
But I'm having a hell of a job trying to figure out what dimensions should be used for the image to add to the contact.
If on the iPhone I take a screenshot and add that manually to a contact then make a call, then the call screen more or less displays the entire screenshot almost the same as the actual desktop. The call screen appears to be slightly magnifying the image.
So whatever size the screenshot is should be close enough for the contact image. I've got an iPhone 14 pro and its UIScreen.main.bounds is 932 by 430. If I export an iPhone screenshot to a Mac, I can see its image size is 2796 by 1290, which is exactly 3 times the bounds size.
So I created an image of size 2796 by 1290 and programmatically added it to a contact (using CNMutableContact.imageData = myUIImage.pngData(). But when a call arrives the image that gets displayed on the call screen is way way way out of whack and alignment. Same too if I add am image of size 932 by 430 (i.e. without the 3 times factor).
I've done lots of experiments but I just can't figure out what size image I should add to the contact. Does anybody happen to know?
(I exported the contact where I manually added the screenshot image as a .vcf to see what image size they use, but it doesn't export the full image that's actually displayed during a call screen, it just exports a truncation of the full image which is a square of 1200 by 1200.)