Rotating image by 3*Double.pi/2 makes image not appear (swift3)

Question

Trying to rotate my image orientation by 270 degrees I can rotate by 90 degrees and the image appears however when rotating the image by 270 nothing happens. I have added 2

Answer 1

You can extend CIImage instead of UIImage and use core image filter CIAffineTransform using the transformation matrix. Start translating it to the center, rotate it 90 degrees (.pi/2) and move it back:

extension CIImage {
    var image: UIImage? { return UIImage(ciImage: self) }
    func rotated(_ angle: CGFloat) -> CIImage? {
        let transform = CGAffineTransform(translationX: extent.midX, y: extent.midY)
            .rotated(by: angle * .pi /  180)
            .translatedBy(x: -extent.midX, y: -extent.midY)
        return CIFilter(name: "CIAffineTransform", withInputParameters: [kCIInputImageKey: self, kCIInputTransformKey: NSValue(cgAffineTransform: transform)])?.outputImage
    }
    var rotatedLeft: CIImage? { return rotated(90) }
    var rotatedRight: CIImage? { return rotated(-90) }
}

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Playground testing:

let image = UIImage(data: try! Data(contentsOf: URL(string:"https://i.stack.imgur.com/Xs4RX.jpg")!))!
image.ciimage?.rotated(22.5)?.image
image.ciimage?.rotatedRight?.image
image.ciimage?.rotatedLeft?.image