How to crop wide images in swift without stretching - ios

Question

I am having trouble cropping pictures taken to be of an exact size that is in the wide format. For instance I take a picture with an iPad front camera, which has the resolution of 960w,1280h and I need to crop to be exactly 875w,570h. I tried some of the methods in here, but they all stretch the image or don't get the size I want.
Here is the first method that I tried:
func cropToBounds(image: UIImage, width: Double, height: Double) -> UIImage {
let cgimage = image.cgImage!
let contextImage: UIImage = UIImage(cgImage: cgimage)
guard let newCgImage = contextImage.cgImage else { return contextImage }
let contextSize: CGSize = contextImage.size
var posX: CGFloat = 0.0
var posY: CGFloat = 0.0
let cropAspect: CGFloat = CGFloat(width / height)
var cropWidth: CGFloat = CGFloat(width)
var cropHeight: CGFloat = CGFloat(height)
if width > height { //Landscape
cropWidth = contextSize.width
cropHeight = contextSize.width / cropAspect
posY = (contextSize.height - cropHeight) / 2
} else if width < height { //Portrait
cropHeight = contextSize.height
cropWidth = contextSize.height * cropAspect
posX = (contextSize.width - cropWidth) / 2
} else { //Square
if contextSize.width >= contextSize.height { //Square on landscape (or square)
cropHeight = contextSize.height
cropWidth = contextSize.height * cropAspect
posX = (contextSize.width - cropWidth) / 2
}else{ //Square on portrait
cropWidth = contextSize.width
cropHeight = contextSize.width / cropAspect
posY = (contextSize.height - cropHeight) / 2
}
}
let rect: CGRect = CGRect(x: posX, y: posY, width: cropWidth, height: cropHeight)
// Create bitmap image from context using the rect
guard let imageRef: CGImage = newCgImage.cropping(to: rect) else { return contextImage}
// Create a new image based on the imageRef and rotate back to the original orientation
let cropped: UIImage = UIImage(cgImage: imageRef, scale: image.scale, orientation: image.imageOrientation)
print(image.scale)
UIGraphicsBeginImageContextWithOptions(CGSize(width: width, height: height), false, 0.0)
cropped.draw(in: CGRect(x: 0, y: 0, width: width, height: height))
let resized = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return resized ?? image
}
This always stretches the image.
I thought about trying to cut the exact size I wanted, so I tried this:
func cropImage(image: UIImage, width: Double, height: Double)->UIImage{
let cgimage = image.cgImage!
let contextImage: UIImage = UIImage(cgImage: cgimage)
let contextSize: CGSize = contextImage.size
var posX: CGFloat = 0.0
var posY: CGFloat = 0.0
var recWidth : CGFloat = CGFloat(width)
var recHeight : CGFloat = CGFloat(height)
if width > height { //Landscape
posY = (contextSize.height - recHeight) / 2
}
else { //Square
posX = (contextSize.width - recWidth) / 2
}
let rect: CGRect = CGRect(x: posX, y: posY, width: recWidth, height: recHeight)
let imageRef:CGImage = cgimage.cropping(to: rect)!
print(imageRef.width)
print(imageRef.height)
let croppedimage:UIImage = UIImage(cgImage: imageRef, scale: image.scale, orientation: image.imageOrientation)
print(croppedimage.size)
return croppedimage
}
But this resulted in an image with the opposite of what I want, 570w,875h. So I thought about inverting the values, but if I do that I get 605w, 570h. Maybe the problem is in how I get the X and Y positions of the image?
EDIT
Here is what I am doing now after the help of Leo Dabus:
extension UIImage {
func cropped(to size: CGSize) -> UIImage? {
guard let cgImage = cgImage?
.cropping(to: .init(origin: .init(x: (self.size.width-size.width)/2,
y: (self.size.height-size.height)/2),
size: size)) else { return nil }
let format = imageRendererFormat
return UIGraphicsImageRenderer(size: size, format: format).image {
_ in
UIImage(cgImage: cgImage, scale: 1, orientation: imageOrientation)
.draw(in: .init(origin: .zero, size: size))
}
}
}
This is how I call it:
let foto = UIImage(data: imageData)!
let size = CGSize(width: 875.0, height: 570.0)
let cropedPhoto = foto.cropped(to: size)
The imageData comes from a capture of the front camera.
And this is my capture code:
#objc func takePhoto(_ sender: Any?) {
let videoOrientation = AVCaptureVideoOrientation.portrait
stillImageOutput!.connection(with: .video)?.videoOrientation = videoOrientation
let settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])
let gesture = previewView.gestureRecognizers
previewView.removeGestureRecognizer(gesture![0])
}
func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
guard let imageData = photo.fileDataRepresentation()
else { return }
}

Answer 1

You just need to get the original size width subtract the destination size width, divide by two and set the cropping origin x value. Next do the same with the height and set the y position. Then just initialize a new UIImage with the cropped cgImage:
extension UIImage {
func cropped(to size: CGSize) -> UIImage? {
guard let cgImage = cgImage?
.cropping(to: .init(origin: .init(x: (self.size.width - size.width) / 2,
y: (self.size.height - size.height) / 2),
size: size)) else { return nil }
return UIImage(cgImage: cgImage, scale: 1, orientation: imageOrientation)
}
}
let imageURL = URL(string: "https://www.comendochucruteesalsicha.com.br/wp-content/uploads/2016/09/IMG_5356-960x1280.jpg")!
let image = UIImage(data: try! Data(contentsOf: imageURL))!
let squared = image.cropped(to: .init(width: 875, height: 570))