Question

What are the proper dimensions for a UIBarButtonItem‘s landscapeImagePhone image?

Answer 1

This has not been documented in the “iOS Human Interface Guidelines”:

http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/mobilehig/IconsImages/IconsImages.html

here is my choice: resize the normal portrait image to (17, 17), and use it as the landscapeImagePhone image. You can adjust the (17, 17) size to whatever you want until it looks good, but it should not larger than the standard portrait barButton Image size (20, 20).

// resize the image for landscape
UIImage *settingsImage = [UIImage imageNamed:@"settings"];
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithImage:settingsImage
                                                           landscapeImagePhone:[settingsImage resizedImage:CGSizeMake(17.f, 17.f) interpolationQuality:kCGInterpolationHigh]
                                                                         style:UIBarButtonItemStyleBordered target:self action:@selector(settingsButtonClicked:)];

Note: for the resizedImage method of UIImage, you can find a lot UIImage catalog on GitHub, I use this git: https://github.com/mbcharbonneau/UIImage-Categories
you can remove the UIImage+Alpha and UIImage+Resize since we do not need them