Added support for video gravity

Source/PreviewView.swift

@@ -17,9 +17,32 @@ LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 import UIKit
 import AVFoundation
 
+/// A function to specifty the Preview Layer's videoGravity. Indicates how the video is displayed within a player layer’s bounds rect.
+public enum SwiftyCamVideoGravity {
+
+    /**
+     - Specifies that the video should be stretched to fill the layer’s bounds
+     - Corrsponds to `AVLayerVideoGravityResize`
+    */
+    case resize
+    /**
+     - Specifies that the player should preserve the video’s aspect ratio and fit the video within the layer’s bounds.
+     - Corresponds to `AVLayerVideoGravityResizeAspect`
+     */
+    case resizeAspect
+    /**
+     - Specifies that the player should preserve the video’s aspect ratio and fill the layer’s bounds.
+     - Correponds to `AVLayerVideoGravityResizeAspectFill`
+    */
+    case resizeAspectFill
+}
+
 class PreviewView: UIView {
     
-    override init(frame: CGRect) {
+    private var gravity: SwiftyCamVideoGravity = .resizeAspect
+    
+    init(frame: CGRect, videoGravity: SwiftyCamVideoGravity) {
+        gravity = videoGravity
         super.init(frame: frame)
         self.backgroundColor = UIColor.black
     }
@@ -29,7 +52,16 @@ class PreviewView: UIView {
     }
     
 	var videoPreviewLayer: AVCaptureVideoPreviewLayer {
-		return layer as! AVCaptureVideoPreviewLayer
+        let previewlayer = layer as! AVCaptureVideoPreviewLayer
+        switch gravity {
+        case .resize:
+            previewlayer.videoGravity = AVLayerVideoGravityResize
+        case .resizeAspect:
+            previewlayer.videoGravity = AVLayerVideoGravityResizeAspect
+        case .resizeAspectFill:
+            previewlayer.videoGravity = AVLayerVideoGravityResizeAspectFill
+        }
+		return previewlayer
 	}
 	
 	var session: AVCaptureSession? {

Source/SwiftyCamViewController.swift

@@ -151,6 +151,8 @@ open class SwiftyCamViewController: UIViewController {
     
     public var allowAutoRotate                = false
     
+    public var videoGravity                   : SwiftyCamVideoGravity = .resizeAspect
+
 
 	// MARK: Public Get-only Variable Declarations
 
@@ -170,7 +172,7 @@ open class SwiftyCamViewController: UIViewController {
 
 	/// Current Capture Session
 
-	fileprivate let session                      = AVCaptureSession()
+	public let session                           = AVCaptureSession()
 
 	/// Serial queue used for setting up session
 
@@ -242,7 +244,7 @@ open class SwiftyCamViewController: UIViewController {
 
 	override open func viewDidLoad() {
 		super.viewDidLoad()
-        view = PreviewView(frame: view.frame)
+        view = PreviewView(frame: view.frame, videoGravity: videoGravity)
 		previewLayer = view as! PreviewView!
 
 		// Add Gesture Recognizers