imgformatwithredirect.swift

import MobileCoreServices

extension String {
  func isImageExtension(_ ext: String) -> Bool {
    let uti = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, ext, nil)
    guard let imageUTI = uti?.takeRetainedValue() else { return false }
    return UTTypeConformsTo(imageUTI, kUTTypeImage)
  }
  
  func isImageLink() -> Bool {
    guard let url = NSURL(string: self) else { return false }
    if isImageExtension((self as NSString).pathExtension) { return true }
    
    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = "HEAD"
    let session = NSURLSession.sharedSession()
    
    let result = session.synchronousDataTaskWithRequest(result)
    guard let response = result.1 as? NSHTTPURLRequest else { return false }

    let contentType = response.allHeaderFields["Content-Type"] as? String
    return contentType?.containsString("image") ?? false
    
    return false
  }
}

public extension NSURLSession {
  func synchronousDataTaskWithRequest(request: NSURLRequest) -> (NSData?, NSURLResponse?, NSError?) {
    var data: NSData?
    var response: NSURLResponse?
    var error: NSError?
    
    let semaphore = dispatch_semaphore_create(0)
    
    dataTaskWithRequest(request) {
      data = $0
      response = $1
      error = $2
      dispatch_semaphore_signal(semaphore)
      }.resume()
    
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
    
    return (data, response, error)
  }
}

"http://www.my-image.com/1.jpg".isImageLink()     // true
"http://www.my-image.com/2.jpeg".isImageLink()    // true
"http://www.my-image.com/3.png".isImageLink()     // true
"http://www.my-image.com/4.tff".isImageLink()     // true

"http://graph.facebook.com/67563683055/picture".isImageLink()   // true