iPhone 6 plus uses @3x image assets, but iPhone 6 uses @2x image assets - just like iPhone 4 and iPhone 5 (Image resolution for new iPhone 6 and 6+, @3x support added?).
iPhone 5, iPhone 5C and iPhone 5S have the screen resolution 640x1136. The screen resolution of iPhone 6 is 750x1334.
So iPhone 6 will scale up images from 640x1136? Is there any way to make graphics customised for iPhone 6's slightly higher screen resolution?
Edit: I know that the PPI is the same. But say for example I want to have an image take up all available width on both iPhone 5 and iPhone 6. I create a 640x200 px image and name it my_image@2x.png. On the iPhone 6 it's going to be upscaled to 750 pixels width, no?
iPhone 6 uses @2x image assets and not R4 or something else because apple didn't provide suitable APIs for background images!
The most direct way now is to create 2 assets and programatically load them :(
Check this out: How to specify size for iPhone 6/7 customised edge-to-edge image?
iPhone 6 (not plus) has the same DPI as iPhone 4 - 5s, i.e. 326 dpi. So, 2x images still actual.
Marat AL is correct reffer to this thread To add to his answer
iPhone 6 might have different resolution but has same density of per pixel inch (PPI)
- Resolution concerns an absolute number of pixels.
- Density (aka Pixels per inch - PPI) concerns a relative number of pixels per inch which is same in case of iPhone 6 and previous iPhones , but different in iPhone 6 plus.
Check more about this here in this thread
Hence iPhone 6 uses @2x image same as iPhones 4 , 5 and 5S.
This post will definitely clear all your confusion regarding iPhone 6 resolution
Edit
This post will helped me to understand better about pixelling and scaling iPhone 6 and 6 plus
来源：https://stackoverflow.com/questions/25871033/why-does-iphone-6-use-2x-image-assets