Developer James Thompson has found an interesting behavior in the latest iOS 8 beta, giving even more weight to the reports that indicate the iPhone 6 will feature a new resolution, featuring a new ‘pixel-tripling’ scaling factor of 3. In May, 9to5Mac first broke news of Apple testing a new screen resolution for an upcoming iPhone, which used a 3x screen scale for content.
Interesting… UIImage on iOS 8b5 will load a @3x image in preference to an @2x one, even on a @2x device. Not so on iOS 7. Bug, but also hmm…— James Thomson (@jamesthomson) August 29, 2014
The behavior is inconsistent, as iOS 8 beta 5 does not always load these 3x assets. However, it reliably chooses the 3x image on 2x devices using the ‘initWithContentsOfFile’ method. After seeing Thompson’s discovery, 9to5Mac has independently confirmed that this is indeed the case.
The code used to replicate the behavior.
Using a set of test images with @1x, @2x and @3x prefixes, the code will always load the 3x asset, even though — per documentation — it should select the image for the current device’s screen scale. For clarity, each test image is numbered for which scale it represents. Thus, the number 3 in the iOS Simulator shows that iOS has selected the image suitable for a 3x screen scale.
To get an idea of the relative sharpness of 1x, 2x and 3x sizes, see the image above for a reasonable approximation. The difference is rather striking. The 1x image is extremely pixellated, the 2x has imperfections with curves but the 3x asset is perfectly smooth.
Moreover, the code path does not accept any arbitrary scale. Testing with other sizes, such as 4x or even 8x, does nothing. The routine specifically chooses 3x image assets. This suggests this behavior is not simply a bug, but is representative of upcoming iPhone features. The implementation of the API specifically looks for @3x assets only. This likely foreshadows what Apple is readying for its new iPhones.
Therefore, this is strong evidence that the next iPhone (or at least, an imminent iOS device) will use a screen with a 3x scale. Unfortunately, this does not help pinpoint a specific resolution, aside from reaffirm that the new iPhones will have significantly more pixels than found in the iPhone 5s. 9to5Mac has reported on Apple testing both 568×320 and 414×736 logical screen resolutions. At 3x, the actual screen resolution of the device would be 1704×960 or 1242×2208. For comparison, the screen resolution of an iPhone 5s is 1136×640.