Swift - Write Image from URL to Local File

Question

I\'ve been learning swift rather quickly, and I\'m trying to develop an OS X application that downloads images.

I\'ve been able to parse the JSON I\'m looking for into a

Answer 1

In Swift 3:

Write

do {
    let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
    let fileURL = documentsURL.appendingPathComponent("\(fileName).png")
    if let pngImageData = UIImagePNGRepresentation(image) {
    try pngImageData.write(to: fileURL, options: .atomic)
    }
} catch { }

Read

let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let filePath = documentsURL.appendingPathComponent("\(fileName).png").path
if FileManager.default.fileExists(atPath: filePath) {
    return UIImage(contentsOfFile: filePath)
}

Answer 2

The following code would write a UIImage in the Application Documents directory under the filename 'filename.jpg'

var image = ....  // However you create/get a UIImage
let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String
let destinationPath = documentsPath.stringByAppendingPathComponent("filename.jpg")
UIImageJPEGRepresentation(image,1.0).writeToFile(destinationPath, atomically: true)

Answer 3

UIImagePNGRepresentaton() function had been deprecated. try image.pngData()

Answer 4

Update for swift 5

just change filename.png to something else

func writeImageToDocs(image:UIImage){
    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String

    let destinationPath = URL(fileURLWithPath: documentsPath).appendingPathComponent("filename.png")

    debugPrint("destination path is",destinationPath)

    do {
        try image.pngData()?.write(to: destinationPath)
    } catch {
        debugPrint("writing file error", error)
    }
}

func readImageFromDocs()->UIImage?{
    let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0] as String

    let filePath = URL(fileURLWithPath: documentsPath).appendingPathComponent("filename.png").path
    if FileManager.default.fileExists(atPath: filePath) {
        return UIImage(contentsOfFile: filePath)
    } else {
        return nil
    }
}

Answer 5

@IBAction func savePhoto(_ sender: Any) {

        let imageData = UIImagePNGRepresentation(myImg.image!)
        let compresedImage = UIImage(data: imageData!)
        UIImageWriteToSavedPhotosAlbum(compresedImage!, nil, nil, nil)

        let alert = UIAlertController(title: "Saved", message: "Your image has been saved", preferredStyle: .alert)
        let okAction = UIAlertAction(title: "Ok", style: .default)
        alert.addAction(okAction)
        self.present(alert, animated: true)
    }   
}

Answer 6

In swift 2.0, stringByAppendingPathComponent is unavailable, so the answer changes a bit. Here is what I've done to write a UIImage out to disk.

documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
if let image = UIImage(data: someNSDataRepresentingAnImage) {
    let fileURL = documentsURL.URLByAppendingPathComponent(fileName+".png")
    if let pngImageData = UIImagePNGRepresentation(image) {
        pngImageData.writeToURL(fileURL, atomically: false)
    }
}