How to Handle iPhone Screen Sizes/Resolution for Background Images

Handling different iphone screen sizes/resolution for background images

It all depends on your image:

• If your Image can be stretched, UIImageView will do all the work.
• If only a part of you image should be stretched you should use this:
  
  • imageView.image = [imageView.image resizableImageWithCapInsets:UIEdgeInsetsMake(top, left, bottom, right)];
• If your image can't be stretched you should then do different images for the phones and change them in runtime.

UPDATE

For the last point you could do something like this in your viewDidLoad method:

BOOL isIPhone = [[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone;
BOOL isIPhone5 = isIPhone && ([[UIScreen mainScreen] bounds].size.height > 480.0);
if (isIPhone5) {
   imageView.image = [UIImage imageNamed:@"iphone4image.png"];
} else {
    imageView.image = [UIImage imageNamed:@"iphone5image.png"];
}

Handling new iPhone screen sizes with a background image

Image sizes for new iPhone6/6+ are:

For iPhone 6:

    750 x 1334 (@2x) for portrait
    1334 x 750 (@2x) for landscape

For iPhone 6 Plus:

    1242 x 2208 (@3x) for portrait
    2208 x 1242 (@3x) for landscape

Hope this will help you.

How to support various iphone screen sizes as of 2014?

If you want to support native resolution of iPhone 6/Plus, you need to add launch images (prior to iOS 8) or launch screen xib (iOS 8).

iPhone 4/4S: 640 x 960

iPhone 5/5S: 640 x 1136

iPhone 6: 750 x 1334

iPhont 6 Plus: 1242 x 2208

That means you need to prepare 4 launch images with above resolution if you want to support these devices. You can use iOS simulator to capture screenshots with different resolutions. Your app will run in compatibility mode on new resolution devices if it can't find the launch image of the specific resolution. compatibility mode means your view will be scaled to fit the new screen size when still have the same logical size.

EDIT:

I think op misunderstands what do @2x and @3x mean. The resolution of iPhone 6 is 750(pixels) x 1334(pixels), 326 pixels per inch. This is the REAL resolution. And 375(points) x 667(points) is the logical size if the native resolution is supported. iPhone 6 Plus's resolution is 1242(pixels) x 2208(pixels), 401 pixels per inch and the logical size is 414(points) x 736(points).

This is how images with different resolutions work on iOS device:

Let's say you want to run your app on iPhone 4s, iPhone 5/5S, iPhone 6/plus. First thing you should do is to provide 4 launch images to support native resolutions of these devices. When iOS launch your app, it will check if the app provides the right launch image to support the native resolution of current device. If iOS finds it, then use that in launch time and the logical size of screen is right, your app runs as normal. Otherwise, your app will run in compatibility mode in which all of the views will be scaled.

Suppose there is an image named foo.png in your app of which the logical size is 100(points) x 100(points). You want this image looks same in all the above devices. You should provide 2 versions of this image. One is 200(pixels) x 200 (pixels) and should be named foo.png@2x and the other is 300(pixels) x 300(pixels) named foo.png@3x. If you load this image with [UIImage imageNamed:@"foo"], on devices except iPhone 6 plus, the app will load the image named foo.png@2x. Otherwise the app will load foo.png@3x and sample it down to 300 * 84%(pixels) x 300 * 84%(pixels).

And if you load an image from an url and need to render it on the runtime. Let's say the size you get is {width:100, height:100}, the scale is 1.0. This means the REAL size of this image is 100 * 1.0(pixels) x 100 * 1.0(pixels. If you don't want it to be scaled, you need to calculate the logical size yourself. You do it like this:

UIImage *image = ... // you get it from an url
CGFloat scale = [UIScreen mainScreen].scale;
CGFloat width = image.size.width / scale; 
CGFloat height = image.size.height / scale;
CGRect frame = CGRectMake(50.0f, 50.0f, width, height)];
UIImageView *imageView = [[UIImageView alloc] initWithFrame:frame];
imageView.contentMode = UIViewContentModeCenter;
imageView.image = image;
[self.view addSubview:imageView];

Aspect Ratio of Background Image for iPhone X

Rather than use an image as your launch screen, you should try using a launch storyboard.

This could contain a single view controller that contains a UIImageView, with contentMode = .aspectFill. This will clip some of the image on either side, but this might be acceptable to you.

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