Saving NSImage in Different Formats Locally

Question

I need to allow the user to save an NSImage to a local file.

So I am using those extensions from this SO answer to can save the image in PNG Format

Answer 1

You can create a custom method to allow you to specify any image type and also the directory where you would like to save your NSImage. You can also set a default value to the destination directory as the current directory, so if you don't pass the directory url it will save to the current one:

extension NSImage {
    func save(as fileName: String, fileType: NSBitmapImageRep.FileType = .jpeg, at directory: URL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)) -> Bool {
        guard let tiffRepresentation = tiffRepresentation, directory.isDirectory, !fileName.isEmpty else { return false }
        do {
            try NSBitmapImageRep(data: tiffRepresentation)?
                .representation(using: fileType, properties: [:])?
                .write(to: directory.appendingPathComponent(fileName).appendingPathExtension(fileType.pathExtension))
            return true
        } catch {
            print(error)
            return false
        }
    }
}

---

You will need also to make sure the url passed to your method is a directory url. You can use URL resourceValues method to get the url isDirectoryKey value and check if it is true:

extension URL {
    var isDirectory: Bool {
       return (try? resourceValues(forKeys: [.isDirectoryKey]))?.isDirectory == true
    }
}

---

You can also extend NSBitmapImageRep.FileType to provide the associated file path extension:

extension NSBitmapImageRep.FileType {
    var pathExtension: String {
        switch self {
        case .bmp:
            return "bmp"
        case .gif:
            return "gif"
        case .jpeg:
            return "jpg"
        case .jpeg2000:
            return "jp2"
        case .png:
            return "png"
        case .tiff:
            return "tif"
        }
    }
}

---

Playground Testing:

let desktopDirectory = FileManager.default.urls(for: .desktopDirectory, in: .userDomainMask).first!
// lets change the current directory to the desktop directory
FileManager.default.changeCurrentDirectoryPath(desktopDirectory.path)

// get your nsimage
let picture  = NSImage(contentsOf: URL(string: "https://i.stack.imgur.com/Xs4RX.jpg")!)!

// this will save to the current directory
if picture.save(as: "profile") {
    print("file saved as profile.jpg which is the default type")
}
if picture.save(as: "profile", fileType: .png) {
    print("file saved as profile.png")
}
if picture.save(as: "profile", fileType: .tiff) {
    print("file saved as profile.tif")
}
if picture.save(as: "profile", fileType: .gif) {
    print("file saved as profile.gif")
}
if picture.save(as: "profile", fileType: .jpeg2000) {
    print("file saved as profile.jp2")
}

// you can also chose a choose another directory without the need to change the current directory
let url = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
if picture.save(as: "profile", at: url) {
    print("file saved as profile.jpg at documentDirectory")
}