问题
How to flip the UIImage horizontally, I found UIImageOrientationUpMirrored enumeration value in the UIImage class reference, how to make use of this property to flip UIImage.
回答1:
UIImage* sourceImage = [UIImage imageNamed:@"whatever.png"];
UIImage* flippedImage = [UIImage imageWithCGImage:sourceImage.CGImage
scale:sourceImage.scale
orientation:UIImageOrientationUpMirrored];
回答2:
A very simple way you can achieve this is by creating a UIImageView instead of a UIImage and do the transform on UIImageView.
yourImageView.image =[UIImage imageNamed:@"whatever.png"];
yourImageView.transform = CGAffineTransform(scaleX: -1, y: 1); //Flipped
Hope this helps.
回答3:
Vertical flip is often required to initialise OpenGL texture using glTexImage2d(...). The above proposed tricks do not actually modify image data and will not work in this case. Here is a code to do the actual data flip inspired by https://stackoverflow.com/a/17909372
- (UIImage *)flipImage:(UIImage *)image
{
UIGraphicsBeginImageContext(image.size);
CGContextDrawImage(UIGraphicsGetCurrentContext(),CGRectMake(0.,0., image.size.width, image.size.height),image.CGImage);
UIImage *i = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return i;
}
回答4:
I have tried with imageFlippedForRightToLeftLayoutDirection, and creating a new UIImage with diferent orientations but at least this is the only solution I found for flipping my image
let ciimage: CIImage = CIImage(CGImage: imagenInicial.CGImage!)
let rotada3 = ciimage.imageByApplyingTransform(CGAffineTransformMakeScale(-1, 1))
As you can see in my playground it worked!! :)
And the, of course, let finalImage = UIImage(CIImage: rotada3)
回答5:
As it Image Orientation Defines:
typedef NS_ENUM(NSInteger, UIImageOrientation) {
UIImageOrientationUp, // default orientation
UIImageOrientationDown, // 180 deg rotation
UIImageOrientationLeft, // 90 deg CCW
UIImageOrientationRight, // 90 deg CW
UIImageOrientationUpMirrored, // as above but image mirrored along other axis. horizontal flip
UIImageOrientationDownMirrored, // horizontal flip
UIImageOrientationLeftMirrored, // vertical flip
UIImageOrientationRightMirrored, // vertical flip
};
I made some improvements for more circumstances like handling UIImage from AVCaptureSession.
UIImage* sourceImage = [UIImage imageNamed:@"whatever.png"];
UIImageOrientation flipingOrientation;
if(sourceImage.imageOrientation>=4){
flippedOrientation = sourceImage.imageOrientation - 4;
}else{
flippedOrientation = sourceImage.imageOrientation + 4;
}
UIImage* flippedImage = [UIImage imageWithCGImage:sourceImage.CGImage
scale: sourceImage.scale orientation: flipingOrientation];
回答6:
here's swift version: (I saw this question in comments)
let srcImage = UIImage(named: "imageName")
let flippedImage = UIImage(CGImage: srcImage.CGImage, scale: srcImage.scale, orientation: UIImageOrientation.UpMirrored)
回答7:
This is a solid implementation to mirror/flip an UIImage horizontally, and can apply to the image back and forth. Since it changes the underlying image data, the drawing(like, screenshot) will also change. Tested to work, no quality loss.
func flipImage() -> UIImage? {
UIGraphicsBeginImageContextWithOptions(self.size, false, self.scale)
let bitmap = UIGraphicsGetCurrentContext()!
bitmap.translateBy(x: size.width / 2, y: size.height / 2)
bitmap.scaleBy(x: -1.0, y: -1.0)
bitmap.translateBy(x: -size.width / 2, y: -size.height / 2)
bitmap.draw(self.cgImage!, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image?
}
回答8:
May be this will be of use for some:
UIImageOrientation imageOrientation;
switch (sourceImage.imageOrientation) {
case UIImageOrientationDown:
imageOrientation = UIImageOrientationDownMirrored;
break;
case UIImageOrientationDownMirrored:
imageOrientation = UIImageOrientationDown;
break;
case UIImageOrientationLeft:
imageOrientation = UIImageOrientationLeftMirrored;
break;
case UIImageOrientationLeftMirrored:
imageOrientation = UIImageOrientationLeft;
break;
case UIImageOrientationRight:
imageOrientation = UIImageOrientationRightMirrored;
break;
case UIImageOrientationRightMirrored:
imageOrientation = UIImageOrientationRight;
break;
case UIImageOrientationUp:
imageOrientation = UIImageOrientationUpMirrored;
break;
case UIImageOrientationUpMirrored:
imageOrientation = UIImageOrientationUp;
break;
default:
break;
}
resultImage = [UIImage imageWithCGImage:sourceImage.CGImage scale:sourceImage.scale orientation:imageOrientation];
回答9:
For Swift 3/4:
imageView.transform = CGAffineTransform(scaleX: -1, y: 1)
回答10:
iOS 10+
[myImage imageWithHorizontallyFlippedOrientation];
Swift 4:
let flippedImage = myImage.withHorizontallyFlippedOrientation()
回答11:
A simple extension.
extension UIImage {
var flipped: UIImage {
guard let cgImage = cgImage else {
return self
}
return UIImage(cgImage: cgImage, scale: scale, orientation: .upMirrored)
}
}
Usage:
let image = #imageLiteral(resourceName: "imageName")
let imageView = UIImageView(image: image.flipped)
回答12:
This is a working iOS8/9 compatible version:
UIImage *image = [UIImage imageNamed:name];
if ([[UIApplication sharedApplication] userInterfaceLayoutDirection] == UIUserInterfaceLayoutDirectionRightToLeft) {
if ([image respondsToSelector:@selector(imageFlippedForRightToLeftLayoutDirection)]) {
//iOS9
image = image.imageFlippedForRightToLeftLayoutDirection;
}
else {
//iOS8
CIImage *coreImage = [CIImage imageWithCGImage:image.CGImage];
coreImage = [coreImage imageByApplyingTransform:CGAffineTransformMakeScale(-1, 1)];
image = [UIImage imageWithCIImage:coreImage scale:image.scale orientation:UIImageOrientationUp];
}
}
return image;
回答13:
Tested in Swift 3 and above
Here is the simple solution to achieve this problem with extensions. I test it and it worked. You can mirror in any direction.
extension UIImage {
func imageUpMirror() -> UIImage {
guard let cgImage = cgImage else { return self }
return UIImage(cgImage: cgImage, scale: scale, orientation: .upMirrored)
}
func imageDownMirror() -> UIImage {
guard let cgImage = cgImage else { return self }
return UIImage(cgImage: cgImage, scale: scale, orientation: .downMirrored)
}
func imageLeftMirror() -> UIImage {
guard let cgImage = cgImage else { return self }
return UIImage(cgImage: cgImage, scale: scale, orientation: .leftMirrored)
}
func imageRightMirror() -> UIImage {
guard let cgImage = cgImage else { return self }
return UIImage(cgImage: cgImage, scale: scale, orientation: .rightMirrored)
}
}
Usage for this code
let image = #imageLiteral(resourceName: "imageName")
flipHorizontally = image.imageUpMirror()
So on, You can use other functions.
回答14:
Here's one of the answers above modified and in Swift 3 that i found particularly useful when you have a button that needs to keep flipping the image back and forth.
func flipImage(sourceImage: UIImage,orientation: UIImageOrientation) -> UIImage {
var imageOrientation = orientation
switch sourceImage.imageOrientation {
case UIImageOrientation.down:
imageOrientation = UIImageOrientation.downMirrored;
break;
case UIImageOrientation.downMirrored:
imageOrientation = UIImageOrientation.down;
break;
case UIImageOrientation.left:
imageOrientation = UIImageOrientation.leftMirrored;
break;
case UIImageOrientation.leftMirrored:
imageOrientation = UIImageOrientation.left;
break;
case UIImageOrientation.right:
imageOrientation = UIImageOrientation.rightMirrored;
break;
case UIImageOrientation.rightMirrored:
imageOrientation = UIImageOrientation.right;
break;
case UIImageOrientation.up:
imageOrientation = UIImageOrientation.upMirrored;
break;
case UIImageOrientation.upMirrored:
imageOrientation = UIImageOrientation.up;
break;
}
return UIImage(cgImage: sourceImage.cgImage!, scale: sourceImage.scale, orientation: imageOrientation)
}
Use:
imageToFlip: UIImage = flipImage(sourceImage: imageToFlip, orientation: imageToFlip.imageOrientation)
回答15:
aroth's answer in SWIFT 3:
let sourceImage = UIImage(named: "whatever.png")!
let flippedImage = UIImage(cgImage: sourceImage.cgImage!, scale: sourceImage.scale, orientation: .upMirrored)
回答16:
Swift 4
yourImage.transform = CGAffineTransform(scaleX: -1, y: 1)
回答17:
Due to unwrapping do the following:
let srcImage = UIImage(named: "myimage")!
let flippedImage = UIImage(cgImage: srcImage.cgImage!,
scale: srcImage.scale, orientation: UIImage.Orientation.upMirrored)
回答18:
you can rotate the image as you want using this
SWIFT 4
extension UIImage {
public func imageRotatedByDegrees(degrees: CGFloat, flip: Bool) -> UIImage {
let radiansToDegrees: (CGFloat) -> CGFloat = {
return $0 * (180.0 / CGFloat(M_PI))
}
let degreesToRadians: (CGFloat) -> CGFloat = {
return $0 / 180.0 * CGFloat(M_PI)
}
// calculate the size of the rotated view's containing box for our drawing space
let rotatedViewBox = UIView(frame: CGRect(origin: CGPoint.zero, size: size))
let t = CGAffineTransform(rotationAngle: degreesToRadians(degrees));
rotatedViewBox.transform = t
let rotatedSize = rotatedViewBox.frame.size
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize)
let bitmap = UIGraphicsGetCurrentContext()!
bitmap.translateBy(x: rotatedSize.width / 2.0, y: rotatedSize.height / 2.0)
// Move the origin to the middle of the image so we will rotate and scale around the center.
//CGContextTranslateCTM(bitmap, rotatedSize.width / 2.0, rotatedSize.height / 2.0);
// // Rotate the image context
bitmap.rotate(by: degreesToRadians(degrees))
// CGContextRotateCTM(bitmap, degreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
var yFlip: CGFloat
if(flip){
yFlip = CGFloat(-1.0)
} else {
yFlip = CGFloat(1.0)
}
bitmap.scaleBy(x: yFlip, y: -1.0)
//CGContextScaleCTM(bitmap, yFlip, -1.0)
bitmap.draw(self.cgImage!, in: CGRect.init(x: -size.width / 2, y: -size.height / 2, width: size.width, height: size.height))
// CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage)
let newImage = UIGraphicsGetImageFromCurrentImageContext()!
UIGraphicsEndImageContext()
return newImage
}
}
来源：https://stackoverflow.com/questions/5404706/how-to-flip-uiimage-horizontally