How do you capture full screen camera photos on iOS?

Question

On Snapchat, it allows you to take a full screen camera photo on iOS. The preview is full screen, and the image returned is full screen. There appears to be no cropping/stretching/etc... What you see is what you get.

Now I've looked all over the place, and I can't figure out how this is actually being done, seeing that the iPhone camera always returns an image with an aspect ratio of 4:3. Yes, you can use the camera view transform to have a full screen "preview", but the image returned is still 4:3 and needs to be cropped.

So my question is, how do you take a full screen camera photo on iOS without cropping? If your answer is that it can't be done, then how is Snapchat doing it (or appearing to do it)?

Solution

Snapchat isn't displaying everything the camera is picking up. By cropping a bit from the top/bottom or sides, they can create a 16:9 image from a 4:3 image. This is easy to verify.

1. Open up the snapchat and camera apps so it's easy to switch between them.
2. Place your phone on its side pointed at something with some marks for reference points.
3. Switch between the apps without moving the phone. There is content that you do not see on Snapchat.

Comments

[SnehaK]

How do we know what to crop from the captured image?

[Acey]

Using the screen pixel dimensions, the captured image dimensions, and math