8 Replies
      Latest reply on Dec 30, 2019 10:44 AM by testUser3434
      testUser3434 Level 1 Level 1 (0 points)

        Hi everyone,


        I have an image view which I initialized using following code:


        imageView.frame = CGRect(x: width * (20 / width), y: navigationBar.frame.maxY, width: width * (335 / width), height: width * (335 / width))
        imageView.contentMode = .scaleToFill
        imageView.clipsToBounds = true
        imageView.isUserInteractionEnabled = true

        As you can see, currently the contentMode is set to .scaleToFill. If I use this setting, most of my image look strange though. The scale seems not to fit somehow. If I change the contentMode to .scaleAspectFill, then every image looks fine.


        However, for my use case, it is required to use .scaleToFill. What can I do to do that? And why is it acting strange using .scaleToFill?

        • Re: Imageview - scaleToFill vs. scaleAspectFill
          Claude31 Level 8 Level 8 (7,845 points)

          Imagine you have an image 50 * 100

          And your imageView is 100 * 400.


          With scaleToFill, image will be scaled to be 100 * 400 to fill completely imageView, so much stretched in height (an el Greco painting !).

          With scaleAspectFit, image will be scaled to 100 * 200 (max that can fit preserving the aspect ratio), looking natural but not filling totally.

          With scaleAspectFill, and imageView.clipsToBounds = true, image will not be distorted bu clipped.


          See illustrations here

          h ttps://useyourloaf.com/blog/stretching-redrawing-and-positioning-with-contentmode/


          However, for my use case, it is required to use .scaleToFill.

          Why ?


          Then you have a trade off to do:

          - either accepts image distortion

          - or change the imageView.frame to be proportional to your image (in my example, change imageView to 100 * 200 for instance)

          - or change mode to scaleAspectFill

            • Re: Imageview - scaleToFill vs. scaleAspectFill
              testUser3434 Level 1 Level 1 (0 points)

              Hi Claude31,


              thanks for the reply. I think, I got it. hmm.. but then coming to another problem.

              I want to merge/overlay two images using following code:

              extension UIImage {
                  static func imageByMergingImages(topImage: UIImage, bottomImage: UIImage, scaleForTop: CGFloat = 1.0) -> UIImage {
                      let size = bottomImage.size
                      let container = CGRect(x: 0, y: 0, width: size.width, height: size.height)
                      UIGraphicsBeginImageContextWithOptions(size, false, 2.0)
                      UIGraphicsGetCurrentContext()!.interpolationQuality = .high
                      bottomImage.draw(in: container)
                      let topWidth = size.width / scaleForTop
                      let topHeight = size.height / scaleForTop
                      let topX = (size.width / 2.0) - (topWidth / 2.0)
                      let topY = (size.height / 2.0) - (topHeight / 2.0)
                      topImage.draw(in: CGRect(x: topX, y: topY, width: topWidth, height: topHeight), blendMode: .normal, alpha: 1.0)
                      return UIGraphicsGetImageFromCurrentImageContext()!


              Whenever, my the contentMode is set to .scaleAspectFill, the merged image doesn't look ok. But if I change it to .scaleToFill, then the merged image looks as expected. Any ideas?

                • Re: Imageview - scaleToFill vs. scaleAspectFill
                  Claude31 Level 8 Level 8 (7,845 points)

                  I don't see:

                  - where you set the mode in the extension

                  - how you change the scale. With 1.0, topImage is drawn in container.


                  Maybe you have an image resolution problem (different for the 2 images ?)



                  Where do you call UIGraphicsEndImageContext ?


                  If you could post the complete code of project somewhere of send an email address, that would ease analysis.

                    • Re: Imageview - scaleToFill vs. scaleAspectFill
                      testUser3434 Level 1 Level 1 (0 points)

                      Basically, I have an "original" image view and another image view for cropping an image. The original image view is not touched at all regarding frame, but the cropImageView is.


                      ciImage = CIImage(cgImage: (ZImageCropper.cropImage(ofImageView: cropImageView, withinPoints: [
                                  CGPoint(x: overlay.frame.origin.x, y: overlay.frame.origin.y),   //Start point
                                  CGPoint(x: overlay.frame.maxX, y: overlay.frame.origin.y),
                                  CGPoint(x: overlay.frame.maxX, y: overlay.frame.maxY),
                                  CGPoint(x:  overlay.frame.origin.x, y: overlay.frame.maxY)])?.cgImage)!)


                      I want to merge the image of the original image view and the cropped image view...


                      This is the code to crop the image:

                      public class ZImageCropper {
                          public class func cropImage(ofImageView:UIImageView, withinPoints points:[CGPoint]) -> UIImage? {
                              //Check if there is start and end points exists
                              if points.count >= 2 {
                                  let path = UIBezierPath()
                                  let shapeLayer = CAShapeLayer()
                                  shapeLayer.fillColor = UIColor.clear.cgColor
                                  shapeLayer.lineWidth = 2
                                  var croppedImage:UIImage?
                                  for (index,point) in points.enumerated() {
                                      if index == 0 {
                                          path.move(to: point)
                                      } else if index == points.count-1 {
                                          path.addLine(to: point)
                                          shapeLayer.path = path.cgPath
                                          shapeLayer.fillColor = UIColor.black.cgColor
                                          ofImageView.layer.mask = shapeLayer
                                          UIGraphicsBeginImageContextWithOptions(ofImageView.frame.size, false, 1)
                                          if let currentContext = UIGraphicsGetCurrentContext() {
                                              ofImageView.layer.render(in: currentContext)
                                          let newImage = UIGraphicsGetImageFromCurrentImageContext()
                                          croppedImage = newImage
                                          //Move points
                                      } else {
                                          path.addLine(to: point)
                                  return croppedImage
                              } else {
                                  return nil