How to flip UIImage horizontally with Swift?

问题

The solution to do UIImage flipping is with the Objective-C code:

[UIImage imageWithCGImage:img.CGImage scale:1.0 orientation: UIImageOrientationDownMirrored]

However, imageWithCGImage is not available in Swift! Is there a solution for flipping image horizontally with Swift? Thanks!

回答1:

Most factory methods are converted to initializers in swift. Whenever available, even if the class method is still available, they are preferred. You can use:

    init(CGImage cgImage: CGImage!, scale: CGFloat, orientation: UIImageOrientation)

The usage would look like this:

var image = UIImage(CGImage: img.CGImage, scale: 1.0, orientation: .DownMirrored)

回答2:

In Swift.... (6.3.1)

YourUIImage.transform = CGAffineTransformMakeScale(-1, 1)

This also works with a UIView

回答3:

Changing image orientation parameter is not actually flipping the image in all cases. Image must be redrawn somehow... For example like this:

Swift 3

func flipImageLeftRight(_ image: UIImage) -> UIImage? {

    UIGraphicsBeginImageContextWithOptions(image.size, false, image.scale)
    let context = UIGraphicsGetCurrentContext()!
    context.translateBy(x: image.size.width, y: image.size.height)
    context.scaleBy(x: -image.scale, y: -image.scale)

    context.draw(image.cgImage!, in: CGRect(origin:CGPoint.zero, size: image.size))

    let newImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return newImage
}

回答4:

For me the simplest way was to use the .withHorizontallyFlippedOrientation() instance method of UIImage as follows:

let flippedImage = straightImage.withHorizontallyFlippedOrientation()

Simple one-liners always make me happy :)

回答5:

Swift 4

YOURIMAGEVIEW.transform = CGAffineTransform(scaleX: -1, y: 1)

回答6:

There is couple of similar questions on SO. And I believe it's worth to post solution using CoreImage here too.

Please note: when getting final UIImage, it's necessary to convert to CGImage first to respect extent of CIImage

extension UIImage {
    func imageRotated(by degrees: CGFloat) -> UIImage {

        let orientation = CGImagePropertyOrientation(imageOrientation)
        // Create CIImage respecting image's orientation 
        guard let inputImage = CIImage(image: self)?.oriented(orientation) 
            else { return self }

        // Flip the image itself
        let flip = CGAffineTransform(scaleX: 1, y: -1)
        let outputImage = inputImage.transformed(by: flip)

        // Create CGImage first
        guard let cgImage = CIContext().createCGImage(outputImage, from: outputImage.extent) 
            else { return self }

        // Create output UIImage from CGImage
        return UIImage(cgImage: cgImage)
    }
}

来源：https://stackoverflow.com/questions/24965638/how-to-flip-uiimage-horizontally-with-swift

标签

ios

swift

uiimage

flip