resize.swift

#!/usr/bin/swift sh

/*
Abstract:
Given an image, resize it, creating 1x, 2x and 3x versions for iOS
Internally, we use the `sips` tool to perform this resizing, this is just a nice wrapper.
*/

import Foundation

@discardableResult
func shell(_ args: String...) -> Int32 {
    let task = Process()
    task.launchPath = "/usr/bin/env"
    task.arguments = args
    task.standardOutput = nil // no stdout
    task.launch()
    task.waitUntilExit()
    return task.terminationStatus
}

guard CommandLine.arguments.count > 2 else {
    print("""
    🔨🌅 iOS/Xcode Image File Resizer

    To start, provide:
      -> 🌲 image file path
      -> 📐 size of the 1x image

    For example:
    ./resize.swift my_cool_image.png 24

    About:
      -> Images maintain their aspect ratio
      -> Input image should be at least as large as the @3x output image
      -> Images are output to the same directory as the parent image
      -> output images will have '-gen' on the end, and '@2x' or '@3x' designators
         as needed; 1x images will not have this suffix.
    """)
    exit(0)
}

print("🚴 Running Image Generator...")

let filepath = CommandLine.arguments[1]
let fileURL = URL(fileURLWithPath: filepath)
let filename = fileURL.deletingPathExtension().lastPathComponent
let fileExtension = fileURL.pathExtension
let parentDirectory = fileURL.deletingLastPathComponent()
let desiredSize = CommandLine.arguments[2]
guard let sizeLength = Int(desiredSize) else {
    print("Invalid side length: \(desiredSize), expected an integer")
    exit(1)
}

/// the filename that should be output for the original filename and
/// the desired output image scale
func name(original: String, scale: Int) -> String {
    var current = original + "-gen"
    if scale > 1 {
        current += "@\(scale)x"
    }
    current += ".png"
    return current
}

for scale in 1...3 {
    let newFilename = name(original: filename, scale: scale)
    let newSize = sizeLength * scale
    let newFilepath = parentDirectory.appendingPathComponent(newFilename)
    print(" -> Generating \(newFilename)")
    let result = shell("sips", "-Z", "\(newSize)", filepath, "--out", "\(newFilepath.path)")
    if result != 0 {
        print(" ⏎ Error generating \(newFilename)!")
    }
}

print("🏆 Completed")
exit(0)