I created a Node.js-based utility that uses ImageMagick to automatically generate iOS app icons for use in Cordova projects and native iOS app development projects.
Easily generate iOS app icons
The tool is very easy to use. The only prerequisite is that you have Node.js installed on your computer. Once that's done, simply provide the image as the first argument to the Node-executed script, as follows:
node index sample.png
To use this tool, download it from the Github repository.