问题
I'm tempted to provide the highest resolution icon and let iOS scale it down as necessary. Is this a bad idea, and (if so) why?
回答1:
Yes, it might be bad idea. If your icon art was produced using a vector image editor (e.g., Adobe Illustrator, Adobe Photoshop with vector primitives, Sketch, etc) you best bet is to export all required resolutions yourself. In doing so, you will guarantee the best possible output for each resolution.
Keep in mind that exporting a single high resolution image and then resizing, for each required resolution, using a bitmap editor (e.g., macOS Preview) won't produce the same results.
PS. As already pointed out, I'm not sure your binary will even be accepted by Apple if missing icon data :-(
回答2:
you'll definitely want to produce files of various sizes as required by xCode. You want to make sure that the file presented when the app runs is of a high quality.
There are tools out there that will automatically create all the sizes you need for your app icon. Here is a link to the site that I use: https://makeappicon.com/
Hope that helps!
来源：https://stackoverflow.com/questions/43313117/is-it-really-necessary-to-provide-all-the-different-app-icon-sizes-for-an-ios-ap