Automatically create icon and splash screen resources
$ ionic cordova resources [platform] [options]
Generate perfectly sized icons and splash screens from PNG source images for your Cordova platforms with this command.
The source image for icons should ideally be at least 1024×1024px and located at resources/icon.png. The source image for splash screens should ideally be at least 2732×2732px and located at resources/splash.png. If you used ionic start, there should already be default Ionic resources in the resources/ directory, which you can overwrite.
You can also generate platform-specific icons and splash screens by placing them in the respective resources/<platform>/ directory. For example, to generate an icon for Android, place your image at resources/android/icon.png.
For best results, the splash screen's artwork should roughly fit within a square (1200×1200px) at the center of the image. You can use https://code.ionicframework.com/resources/splash.psd as a template for your splash screen.
ionic cordova resources will automatically update your config.xml to reflect the changes in the generated images, which Cordova then configures.
This command uses the cordova-res utility to generate resources locally.
Cordova reference documentation:
リソースを生成したいプラットフォーム（ios、android）を指定します。
--icon: Generate icon resources (or -i)
--splash: Generate splash screen resources (or -s)
$ ionic cordova resources
$ ionic cordova resources ios
$ ionic cordova resources android