问题
The designers on a project I am responsible for developing (one of my first iOS projects) designed the app using a Photoshop canvas set at 1242x2208 pixels, which is the number of pixels that the iPhone 6+ uses. I've scoured the internet and am just getting more and more confused by all the conversions for 1x, 2x, 3x and to further the confusion, apple downsizes to 1080x1920.
Anyways, how do I cut the assets correctly for @1x, @2x, @3x? When I crop the element I want, I save it out at 3x. But what do I divide by to get the 2x and 1x versions?
Here's secondary question and a hypothetical situation: There is a button that is designed to be the full width of the screen in portrait, so the designer made it 1242x100. If I save it out at 3x, then scale it down for 2 and 1x, will this button fit all the different screen sizes all the way down to iPhone 4/4s, which has a smaller pixel dimension and different aspect ratio?
Confused, any help appreciated!
回答1:
Example: If you original artwork is 960px by 1704px, just save you image including "@3x"
image@3x.png // (960 x 1704)
Then you have to resize it to 640x1136 and save including "2x"
image@2x.png // (640x1136)
And then you have to resize it to 320x568 and save as 1x
image.png // (320x568)
回答2:
Indeed the Retina sizes are confusing, but this is what auto resize is used for in Xcode.
But The API which Apple give us, chooses the @3, @2 and 1 sizes by itself. There isn't anything that the developer/designer needs to do but provide all three images. An example is:
ObjC:
+ (NSImage *)imageNamed:(NSString *)name]
Swift:
init?(named name: String) -> NSImage
Would just use the name of the image without the @ etc... So, myImageName@3x.png myImageName@2x.png myImageName.png would just be referred to as "myImageName"
The API handles the rest :)
回答3:
I have had the same problem. What I did was, after cutting all images for iPhone 6+(@3x), I just resized the PSD to iPhone 5's width which is 640px, (height would be 1138 px if you keep aspect ratio) and cut @2x images. For the 1x images, again resized to 320px width.
Just, iPhone 6+, iPhone 6 and iPhone 5 have almost same aspect ratio.
Good Luck!
来源：https://stackoverflow.com/questions/27559570/how-to-cut-ios8-assets-from-a-psd-designed-at-1242px-by-2208px