Command Line tool to add Rounded Corners to images

roundedCorners.swift

//
// This is a small command line tool for macOS that takes all images in a directory
// and creates versions of these images with rounded corners. Ideal for App Icons.
//
// Compile with:
// $ swiftc roundedCorners.swift
//
// Usage:
// ./roundedCorners imageDirectory
//

import Foundation
import Cocoa

let arguments = CommandLine.arguments

guard arguments.count >= 2 else {
    fatalError("Usage: \(arguments[0]) <path of directory with images>")
}

let currentPathURL = URL(string: FileManager.default.currentDirectoryPath)

guard let inputURL = URL(string: arguments[1]) else {
    fatalError("Invalid input URL")
}

print("Input URL: \(inputURL)")

guard let contents = try? FileManager.default.contentsOfDirectory(at: inputURL, includingPropertiesForKeys: nil) else {
    fatalError("Unable to access input directory")
}

guard !contents.isEmpty else {
    fatalError("Empty directory")
}

for imageURL in contents {
    print("Opening: \(imageURL)")

    if let image = NSImage(contentsOf: imageURL) {

        if let data = makeRoundedImage(image: image) {

            let fileName = imageURL.deletingPathExtension().lastPathComponent
            let newURL = imageURL.deletingLastPathComponent().appending(path: "\(fileName)_rounded.png")
            print("Saving to: \(newURL)")

            do {
                try data.write(to: newURL)
            } catch {
                print("Failed to save image! \(error)")
            }
        } else {
            print("Failed to generate image!")
        }
    } else {
        print("Not an image, skipping...")
    }
}

func makeRoundedImage(image: NSImage, radiusRatio: CGFloat = (360.0/2048.0)) -> Data? {
    guard let size = image.pixelSize else {
        return nil
    }

    guard let rep = NSBitmapImageRep(
        bitmapDataPlanes: nil,
        pixelsWide: Int(size.width),
        pixelsHigh: Int(size.height),
        bitsPerSample: 8,
        samplesPerPixel: 4,
        hasAlpha: true,
        isPlanar: false,
        colorSpaceName: .calibratedRGB,
        bytesPerRow: 0,
        bitsPerPixel: 0
    ) else {
        return nil
    }

    rep.size = size

    guard let context = NSGraphicsContext(bitmapImageRep: rep) else {
        return nil
    }

    let rect = CGRect(origin: CGPoint.zero, size: size)

    let imageLayer = CALayer()
    imageLayer.frame = rect
    imageLayer.contents = image.cgImage(forProposedRect: nil, context: nil, hints: nil)

    imageLayer.masksToBounds = true
    imageLayer.cornerRadius = (radiusRatio * size.width)

    imageLayer.render(in: context.cgContext)
    return rep.representation(using: .png, properties: [:])
}

extension NSImage{
    var pixelSize: NSSize? {
        guard let rep = self.representations.first else { return nil }
        return NSSize(width: rep.pixelsWide, height: rep.pixelsHigh)
    }
}