Como girar uma UIImage 90 graus?

Eu tenho um UIImageque é UIImageOrientationUp(retrato) que eu gostaria de rotação anti-horário em 90 graus (a paisagem). Eu não quero usar a CGAffineTransform. Eu quero que os pixels da UIImageposição realmente mudem. Estou usando um bloco de código (mostrado abaixo) originalmente destinado a redimensionar um UIImagepara fazer isso. Defino um tamanho de destino como o tamanho atual do, UIImagemas recebo um erro:

(Erro): CGBitmapContextCreate: bytes / linha de dados inválidos: deve ser pelo menos 1708 para 8 bits / componente inteiro, 3 componentes, kCGImageAlphaPremultipliedLast.

(Não recebo um erro sempre que forneço um tamanho MENOR como o tamanho alvo BTW). Como rotacionar meus UIImage90 graus no sentido anti-horário usando apenas as principais funções gráficas, preservando o tamanho atual?

-(UIImage*)reverseImageByScalingToSize:(CGSize)targetSize:(UIImage*)anImage
{
    UIImage* sourceImage = anImage; 
    CGFloat targetWidth = targetSize.height;
    CGFloat targetHeight = targetSize.width;

    CGImageRef imageRef = [sourceImage CGImage];
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);

    if (bitmapInfo == kCGImageAlphaNone) {
        bitmapInfo = kCGImageAlphaNoneSkipLast;
    }

    CGContextRef bitmap;

    if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
        bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    } else {


        bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    }       


    if (sourceImage.imageOrientation == UIImageOrientationRight) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);

    } else if (sourceImage.imageOrientation == UIImageOrientationLeft) {
        CGContextRotateCTM (bitmap, radians(-90));
        CGContextTranslateCTM (bitmap, -targetWidth, 0);

    } else if (sourceImage.imageOrientation == UIImageOrientationDown) {
        // NOTHING
    } else if (sourceImage.imageOrientation == UIImageOrientationUp) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);
    }

    CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage* newImage = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return newImage; 
}

Que tal algo como:

static inline double radians (double degrees) {return degrees * M_PI/180;}
UIImage* rotate(UIImage* src, UIImageOrientation orientation)
{
    UIGraphicsBeginImageContext(src.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orientation == UIImageOrientationRight) {
        CGContextRotateCTM (context, radians(90));
    } else if (orientation == UIImageOrientationLeft) {
        CGContextRotateCTM (context, radians(-90));
    } else if (orientation == UIImageOrientationDown) {
        // NOTHING
    } else if (orientation == UIImageOrientationUp) {
        CGContextRotateCTM (context, radians(90));
    }

    [src drawAtPoint:CGPointMake(0, 0)];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

Acredito que a maneira mais fácil (e segura de threads também) é:

//assume that the image is loaded in landscape mode from disk
UIImage * landscapeImage = [UIImage imageNamed:imgname];
UIImage * portraitImage = [[UIImage alloc] initWithCGImage: landscapeImage.CGImage
                                                     scale: 1.0
                                               orientation: UIImageOrientationRight];

Nota: Como o Brainware disse, isso modifica apenas os dados de orientação da imagem - os dados de pixel são intocados. Para alguns aplicativos, isso pode não ser suficiente.

Ou em Swift:

guard
    let landscapeImage = UIImage(named: "imgname"),
    let landscapeCGImage = landscapeImage.cgImage
else { return }
let portraitImage = UIImage(cgImage: landscapeCGImage, scale: landscapeImage.scale, orientation: .right)

Confira o código simples e impressionante de Hardy Macia em: cut-scaling-and-rotating-uiimages

Apenas ligue

UIImage *rotatedImage = [originalImage imageRotatedByDegrees:90.0];

Obrigado Hardy Macia!

Cabeçalho:

• (UIImage *) imageAtRect: (CGRect) rect;
• (UIImage *) imageByScalingProportionallyToMinimumSize: (CGSize) targetSize;
• (UIImage *) imageByScalingProportionallyToSize: (CGSize) targetSize;
• (UIImage *) imageByScalingToSize: (CGSize) targetSize;
• (UIImage *) imageRotatedByRadians: (CGFloat) radianos;
• (UIImage *) imageRotatedByDegrees: graus (CGFloat);

Como o link pode morrer, aqui está o código completo

//
//  UIImage-Extensions.h
//
//  Created by Hardy Macia on 7/1/09.
//  Copyright 2009 Catamount Software. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

@interface UIImage (CS_Extensions)
- (UIImage *)imageAtRect:(CGRect)rect;
- (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize;
- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;
- (UIImage *)imageByScalingToSize:(CGSize)targetSize;
- (UIImage *)imageRotatedByRadians:(CGFloat)radians;
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees;

@end;

//
//  UIImage-Extensions.m
//
//  Created by Hardy Macia on 7/1/09.
//  Copyright 2009 Catamount Software. All rights reserved.
//

#import "UIImage-Extensions.h"

CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;};
CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;};

@implementation UIImage (CS_Extensions)

-(UIImage *)imageAtRect:(CGRect)rect
{

   CGImageRef imageRef = CGImageCreateWithImageInRect([self CGImage], rect);
   UIImage* subImage = [UIImage imageWithCGImage: imageRef];
   CGImageRelease(imageRef);

   return subImage;

}

- (UIImage *)imageByScalingProportionallyToMinimumSize:(CGSize)targetSize {

   UIImage *sourceImage = self;
   UIImage *newImage = nil;

   CGSize imageSize = sourceImage.size;
   CGFloat width = imageSize.width;
   CGFloat height = imageSize.height;

   CGFloat targetWidth = targetSize.width;
   CGFloat targetHeight = targetSize.height;

   CGFloat scaleFactor = 0.0;
   CGFloat scaledWidth = targetWidth;
   CGFloat scaledHeight = targetHeight;

   CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

   if (CGSizeEqualToSize(imageSize, targetSize) == NO) {

      CGFloat widthFactor = targetWidth / width;
      CGFloat heightFactor = targetHeight / height;

      if (widthFactor > heightFactor) 
         scaleFactor = widthFactor;
      else
         scaleFactor = heightFactor;

      scaledWidth  = width * scaleFactor;
      scaledHeight = height * scaleFactor;

      // center the image

      if (widthFactor > heightFactor) {
         thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
      } else if (widthFactor < heightFactor) {
         thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
      }
   }


   // this is actually the interesting part:

   UIGraphicsBeginImageContext(targetSize);

   CGRect thumbnailRect = CGRectZero;
   thumbnailRect.origin = thumbnailPoint;
   thumbnailRect.size.width  = scaledWidth;
   thumbnailRect.size.height = scaledHeight;

   [sourceImage drawInRect:thumbnailRect];

   newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   if(newImage == nil) NSLog(@"could not scale image");


   return newImage ;
}


- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize {

   UIImage *sourceImage = self;
   UIImage *newImage = nil;

   CGSize imageSize = sourceImage.size;
   CGFloat width = imageSize.width;
   CGFloat height = imageSize.height;

   CGFloat targetWidth = targetSize.width;
   CGFloat targetHeight = targetSize.height;

   CGFloat scaleFactor = 0.0;
   CGFloat scaledWidth = targetWidth;
   CGFloat scaledHeight = targetHeight;

   CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

   if (CGSizeEqualToSize(imageSize, targetSize) == NO) {

      CGFloat widthFactor = targetWidth / width;
      CGFloat heightFactor = targetHeight / height;

      if (widthFactor < heightFactor) 
         scaleFactor = widthFactor;
      else
         scaleFactor = heightFactor;

      scaledWidth  = width * scaleFactor;
      scaledHeight = height * scaleFactor;

      // center the image

      if (widthFactor < heightFactor) {
         thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
      } else if (widthFactor > heightFactor) {
         thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
      }
   }


   // this is actually the interesting part:

   UIGraphicsBeginImageContext(targetSize);

   CGRect thumbnailRect = CGRectZero;
   thumbnailRect.origin = thumbnailPoint;
   thumbnailRect.size.width  = scaledWidth;
   thumbnailRect.size.height = scaledHeight;

   [sourceImage drawInRect:thumbnailRect];

   newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   if(newImage == nil) NSLog(@"could not scale image");


   return newImage ;
}


- (UIImage *)imageByScalingToSize:(CGSize)targetSize {

   UIImage *sourceImage = self;
   UIImage *newImage = nil;

   //   CGSize imageSize = sourceImage.size;
   //   CGFloat width = imageSize.width;
   //   CGFloat height = imageSize.height;

   CGFloat targetWidth = targetSize.width;
   CGFloat targetHeight = targetSize.height;

   //   CGFloat scaleFactor = 0.0;
   CGFloat scaledWidth = targetWidth;
   CGFloat scaledHeight = targetHeight;

   CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

   // this is actually the interesting part:

   UIGraphicsBeginImageContext(targetSize);

   CGRect thumbnailRect = CGRectZero;
   thumbnailRect.origin = thumbnailPoint;
   thumbnailRect.size.width  = scaledWidth;
   thumbnailRect.size.height = scaledHeight;

   [sourceImage drawInRect:thumbnailRect];

   newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   if(newImage == nil) NSLog(@"could not scale image");


   return newImage ;
}


- (UIImage *)imageRotatedByRadians:(CGFloat)radians
{
   return [self imageRotatedByDegrees:RadiansToDegrees(radians)];
}

- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees 
{   
   // calculate the size of the rotated view's containing box for our drawing space
   UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
   CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
   rotatedViewBox.transform = t;
   CGSize rotatedSize = rotatedViewBox.frame.size;
   [rotatedViewBox release];

   // Create the bitmap context
   UIGraphicsBeginImageContext(rotatedSize);
   CGContextRef bitmap = UIGraphicsGetCurrentContext();

   // Move the origin to the middle of the image so we will rotate and scale around the center.
   CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

   //   // Rotate the image context
   CGContextRotateCTM(bitmap, DegreesToRadians(degrees));

   // Now, draw the rotated/scaled image into the context
   CGContextScaleCTM(bitmap, 1.0, -1.0);
   CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);

   UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();
   return newImage;

}

@end;

Por mais estranho que isso pareça, o código a seguir resolveu o problema para mim:

+ (UIImage*)unrotateImage:(UIImage*)image {
    CGSize size = image.size;
    UIGraphicsBeginImageContext(size);
    [image drawInRect:CGRectMake(0,0,size.width ,size.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

Uma função de rotação segura da linha é a seguinte (funciona muito melhor):

-(UIImage*)imageByRotatingImage:(UIImage*)initImage fromImageOrientation:(UIImageOrientation)orientation
{
CGImageRef imgRef = initImage.CGImage;

CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);

CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = orientation;
switch(orient) {

    case UIImageOrientationUp: //EXIF = 1
        return initImage;
        break;

    case UIImageOrientationUpMirrored: //EXIF = 2
        transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        break;

    case UIImageOrientationDown: //EXIF = 3
        transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
        transform = CGAffineTransformRotate(transform, M_PI);
        break;

    case UIImageOrientationDownMirrored: //EXIF = 4
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
        transform = CGAffineTransformScale(transform, 1.0, -1.0);
        break;

    case UIImageOrientationLeftMirrored: //EXIF = 5
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationLeft: //EXIF = 6
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationRightMirrored: //EXIF = 7
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeScale(-1.0, 1.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    case UIImageOrientationRight: //EXIF = 8
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    default:
        [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

}
// Create the bitmap context
CGContextRef    context = NULL;
void *          bitmapData;
int             bitmapByteCount;
int             bitmapBytesPerRow;

// Declare the number of bytes per row. Each pixel in the bitmap in this
// example is represented by 4 bytes; 8 bits each of red, green, blue, and
// alpha.
bitmapBytesPerRow   = (bounds.size.width * 4);
bitmapByteCount     = (bitmapBytesPerRow * bounds.size.height);
bitmapData = malloc( bitmapByteCount );
if (bitmapData == NULL)
{
    return nil;
}

// Create the bitmap context. We want pre-multiplied ARGB, 8-bits
// per component. Regardless of what the source image format is
// (CMYK, Grayscale, and so on) it will be converted over to the format
// specified here by CGBitmapContextCreate.
CGColorSpaceRef colorspace = CGImageGetColorSpace(imgRef);
context = CGBitmapContextCreate (bitmapData,bounds.size.width,bounds.size.height,8,bitmapBytesPerRow,
                                 colorspace, kCGBitmapAlphaInfoMask & kCGImageAlphaPremultipliedLast);

if (context == NULL)
    // error creating context
    return nil;

CGContextScaleCTM(context, -1.0, -1.0);
CGContextTranslateCTM(context, -bounds.size.width, -bounds.size.height);

CGContextConcatCTM(context, transform);

// Draw the image to the bitmap context. Once we draw, the memory
// allocated for the context for rendering will then contain the
// raw image data in the specified color space.
CGContextDrawImage(context, CGRectMake(0,0,width, height), imgRef);

CGImageRef imgRef2 = CGBitmapContextCreateImage(context);
CGContextRelease(context);
free(bitmapData);
UIImage * image = [UIImage imageWithCGImage:imgRef2 scale:initImage.scale orientation:UIImageOrientationUp];
CGImageRelease(imgRef2);
return image;
}

Eu tive problemas com todos os itens acima, incluindo a resposta aprovada. Eu converti a categoria de Hardy novamente em um método, pois tudo que eu queria era girar uma imagem. Aqui está o código e o uso:

- (UIImage *)imageRotatedByDegrees:(UIImage*)oldImage deg:(CGFloat)degrees{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,oldImage.size.width, oldImage.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(degrees * M_PI / 180);
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();

// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

//   // Rotate the image context
CGContextRotateCTM(bitmap, (degrees * M_PI / 180));

// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-oldImage.size.width / 2, -oldImage.size.height / 2, oldImage.size.width, oldImage.size.height), [oldImage CGImage]);

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}

E o uso:

UIImage *image2 = [self imageRotatedByDegrees:image deg:90];

Obrigado Hardy!

Girar a imagem em 90 graus (sentido horário / anti-horário)

Chamada de função -

 UIImage *rotatedImage = [self rotateImage:originalImage clockwise:YES];

Implementação:

- (UIImage*)rotateImage:(UIImage*)sourceImage clockwise:(BOOL)clockwise
  {
    CGSize size = sourceImage.size;
    UIGraphicsBeginImageContext(CGSizeMake(size.height, size.width));
    [[UIImage imageWithCGImage:[sourceImage CGImage]
                         scale:1.0
                   orientation:clockwise ? UIImageOrientationRight : UIImageOrientationLeft]
                   drawInRect:CGRectMake(0,0,size.height ,size.width)];

   UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

   return newImage;
  }

Se você deseja adicionar um botão de rotação da foto que continuará girando a foto em incrementos de 90 graus, aqui está. ( finalImageé uma UIImage que já foi criada em outro lugar.)

- (void)rotatePhoto {
    UIImage *rotatedImage;

    if (finalImage.imageOrientation == UIImageOrientationRight)
        rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
                                              scale: 1.0
                                        orientation: UIImageOrientationDown];
    else if (finalImage.imageOrientation == UIImageOrientationDown)
        rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
                                              scale: 1.0
                                        orientation: UIImageOrientationLeft];
    else if (finalImage.imageOrientation == UIImageOrientationLeft)
        rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
                                              scale: 1.0
                                        orientation: UIImageOrientationUp];
    else
        rotatedImage = [[UIImage alloc] initWithCGImage: finalImage.CGImage
                                                     scale: 1.0
                                               orientation: UIImageOrientationRight];
    finalImage = rotatedImage;
}

Simples. Apenas mude a bandeira de orientação da imagem.

UIImage *oldImage = [UIImage imageNamed:@"whatever.jpg"];
UIImageOrientation newOrientation;
switch (oldImage.imageOrientation) {
    case UIImageOrientationUp:
        newOrientation = UIImageOrientationLandscapeLeft;
        break;
    case UIImageOrientationLandscapeLeft:
        newOrientation = UIImageOrientationDown;
        break;
    case UIImageOrientationDown:
        newOrientation = UIImageOrientationLandscapeRight;
        break;
    case UIImageOrientationLandscapeRight:
        newOrientation = UIImageOrientationUp;
        break;
    // you can also handle mirrored orientations similarly ...
}
UIImage *rotatedImage = [UIImage imageWithCGImage:oldImage.CGImage scale:1.0f orientation:newOrientation];

Aqui está uma extensão Swift para UIImage que gira a imagem por qualquer ângulo arbitrário. Usá-lo como este: let rotatedImage = image.rotated(byDegrees: degree). Usei o código Objective-C em uma das outras respostas e removi algumas linhas que estavam incorretas (material da caixa girada) e o transformei em uma extensão para o UIImage.

extension UIImage {

func rotate(byDegrees degree: Double) -> UIImage {
    let radians = CGFloat(degree*M_PI)/180.0 as CGFloat
    let rotatedSize = self.size
    let scale = UIScreen.mainScreen().scale
    UIGraphicsBeginImageContextWithOptions(rotatedSize, false, scale)
    let bitmap = UIGraphicsGetCurrentContext()
    CGContextTranslateCTM(bitmap, rotatedSize.width / 2, rotatedSize.height / 2);
    CGContextRotateCTM(bitmap, radians);
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2 , self.size.width, self.size.height), self.CGImage );
    let newImage = UIGraphicsGetImageFromCurrentImageContext()

    return newImage
}
}

Extensão Swift 3 UIImage:

func fixOrientation() -> UIImage {

    // No-op if the orientation is already correct
    if ( self.imageOrientation == .up ) {
        return self;
    }

    // We need to calculate the proper transformation to make the image upright.
    // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
    var transform: CGAffineTransform = .identity

    if ( self.imageOrientation == .down || self.imageOrientation == .downMirrored ) {
        transform = transform.translatedBy(x: self.size.width, y: self.size.height)
        transform = transform.rotated(by: .pi)
    }

    if ( self.imageOrientation == .left || self.imageOrientation == .leftMirrored ) {
        transform = transform.translatedBy(x: self.size.width, y: 0)
        transform = transform.rotated(by: .pi/2)
    }

    if ( self.imageOrientation == .right || self.imageOrientation == .rightMirrored ) {
        transform = transform.translatedBy(x: 0, y: self.size.height);
        transform = transform.rotated(by: -.pi/2);
    }

    if ( self.imageOrientation == .upMirrored || self.imageOrientation == .downMirrored ) {
        transform = transform.translatedBy(x: self.size.width, y: 0)
        transform = transform.scaledBy(x: -1, y: 1)
    }

    if ( self.imageOrientation == .leftMirrored || self.imageOrientation == .rightMirrored ) {
        transform = transform.translatedBy(x: self.size.height, y: 0);
        transform = transform.scaledBy(x: -1, y: 1);
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    let ctx: CGContext = CGContext(data: nil, width: Int(self.size.width), height: Int(self.size.height),
                                   bitsPerComponent: self.cgImage!.bitsPerComponent, bytesPerRow: 0,
                                   space: self.cgImage!.colorSpace!,
                                   bitmapInfo: self.cgImage!.bitmapInfo.rawValue)!;

    ctx.concatenate(transform)

    if ( self.imageOrientation == .left ||
        self.imageOrientation == .leftMirrored ||
        self.imageOrientation == .right ||
        self.imageOrientation == .rightMirrored ) {
        ctx.draw(self.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: self.size.height,height: self.size.width))
    } else {
        ctx.draw(self.cgImage!, in: CGRect(x: 0.0,y: 0.0,width: self.size.width,height: self.size.height))
    }

    // And now we just create a new UIImage from the drawing context and return it
    return UIImage(cgImage: ctx.makeImage()!)
}

Versão Swift 4.2 da resposta do RawMean :

extension UIImage {

func rotated(byDegrees degree: Double) -> UIImage {
    let radians = CGFloat(degree * .pi) / 180.0 as CGFloat
    let rotatedSize = self.size
    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(rotatedSize, false, scale)
    let bitmap = UIGraphicsGetCurrentContext()
    bitmap?.translateBy(x: rotatedSize.width / 2, y: rotatedSize.height / 2)
    bitmap?.rotate(by: radians)
    bitmap?.scaleBy(x: 1.0, y: -1.0)
    bitmap?.draw(
        self.cgImage!,
        in: CGRect.init(x: -self.size.width / 2, y: -self.size.height / 2 , width: self.size.width, height: self.size.height))
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext() // this is needed
    return newImage!
}

}

Eu tento esse código, ele funciona e foi extraído de http://www.catamount.com/blog/1015/uiimage-extensions-for-cutting-scaling-and-rotating-uiimages/

+ (UIImage *)rotateImage:(UIImage*)src byRadian:(CGFloat)radian
{
    // calculate the size of the rotated view's containing box for our drawing space
    UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0, src.size.width, src.size.height)];
    CGAffineTransform t = CGAffineTransformMakeRotation(radian);
    rotatedViewBox.transform = t;
    CGSize rotatedSize = rotatedViewBox.frame.size;

    // Create the bitmap context
    UIGraphicsBeginImageContext(rotatedSize);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();

    // Move the origin to the middle of the image so we will rotate and scale around the center.
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

    //   // Rotate the image context
    CGContextRotateCTM(bitmap, radian);

    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-src.size.width / 2, -src.size.height / 2, src.size.width, src.size.height), [src CGImage]);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

Pequenas alterações nas outras respostas baseadas no código de Hardy Macia. Não há necessidade de criar um UIViewobjeto inteiro simplesmente para calcular o retângulo delimitador da imagem girada. Basta aplicar uma transformação de rotação ao retângulo da imagem usando CGRectApplyAffineTransform.

static CGFloat DegreesToRadians(CGFloat degrees) {return degrees * M_PI / 180;}
static CGFloat RadiansToDegrees(CGFloat radians) {return radians * 180/M_PI;}


- (CGSize)rotatedImageSize:(CGFloat)degrees
{
    CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
    CGRect originalImageRect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGRect rotatedImageRect = CGRectApplyAffineTransform(originalImageRect, t);
    CGSize rotatedSize = rotatedImageRect.size;

    return rotatedSize;
}

- (UIImage*)imageRotatedByDegrees:(CGFloat)degrees
{
    // calculate the size of the rotated view's containing box for our drawing space
    CGSize rotatedSize = [self rotatedImageSize:degrees];

    // Create the bitmap context
    UIGraphicsBeginImageContext(rotatedSize);
    CGContextRef bitmap = UIGraphicsGetCurrentContext();

    // Move the origin to the middle of the image so we will rotate and scale around the center.
    CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);

    //   // Rotate the image context
    CGContextRotateCTM(bitmap, DegreesToRadians(degrees));

    // Now, draw the rotated/scaled image into the context
    CGContextScaleCTM(bitmap, 1.0, -1.0);
    CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);

    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

"tint uiimage greayscale" parece ser o Google-Fu apropriado para este

imediatamente eu recebo:

https://discussions.apple.com/message/8104516?messageID=8104516ꩄ

https://discussions.apple.com/thread/2751445?start=0&tstart=0

Como pintar uma imagem programaticamente no iPhone?

Gosto da elegância simples da Peter Sarnowskiresposta, mas ela pode causar problemas quando você não pode confiar nos EXIFmetadados e coisas do gênero. Nas situações em que você precisa rotacionar os dados da imagem real, eu recomendaria algo como isto:

- (UIImage *)rotateImage:(UIImage *) img
{
    CGSize imgSize = [img size];
    UIGraphicsBeginImageContext(imgSize);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextRotateCTM(context, M_PI_2);
    CGContextTranslateCTM(context, 0, -640);
    [img drawInRect:CGRectMake(0, 0, imgSize.height, imgSize.width)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

O código acima pega uma imagem cuja orientação é Landscape(não se lembra se é Landscape Leftou Landscape Right) e a rotaciona Portrait. É um exemplo que pode ser modificado para suas necessidades.

Os principais argumentos com os quais você teria que brincar são CGContextRotateCTM(context, M_PI_2)onde você decide quanto deseja girar, mas depois precisa se certificar de que a imagem ainda seja desenhada na tela usando CGContextTranslateCTM(context, 0, -640). Esta última parte é muito importante para garantir que você veja a imagem e não uma tela em branco.

Para mais informações, consulte a fonte .

resize-a-uiimage-the-right-way explica alguns dos problemas que muitos exemplos de código têm para fazer isso e possui alguns trechos de código para ajudar a lidar com o UIImages - o método auxiliar privado no UIImage + resize.m aceita uma transformação para permitir rotação, então você só precisa expor isso como uma interface pública.

// Returns a copy of the image that has been transformed using the given affine transform and scaled to the new size
// The new image's orientation will be UIImageOrientationUp, regardless of the current image's orientation
// If the new size is not integral, it will be rounded up
- (UIImage *)resizedImage:(CGSize)newSize
                transform:(CGAffineTransform)transform
           drawTransposed:(BOOL)transpose
     interpolationQuality:(CGInterpolationQuality)quality {
    CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height));
    CGRect transposedRect = CGRectMake(0, 0, newRect.size.height, newRect.size.width);
    CGImageRef imageRef = self.CGImage;

    // Build a context that's the same dimensions as the new size
    CGContextRef bitmap = CGBitmapContextCreate(NULL,
                                                newRect.size.width,
                                                newRect.size.height,
                                                CGImageGetBitsPerComponent(imageRef),
                                                0,
                                                CGImageGetColorSpace(imageRef),
                                                CGImageGetBitmapInfo(imageRef));

    // Rotate and/or flip the image if required by its orientation
    CGContextConcatCTM(bitmap, transform);

    // Set the quality level to use when rescaling
    CGContextSetInterpolationQuality(bitmap, quality);

    // Draw into the context; this scales the image
    CGContextDrawImage(bitmap, transpose ? transposedRect : newRect, imageRef);

    // Get the resized image from the context and a UIImage
    CGImageRef newImageRef = CGBitmapContextCreateImage(bitmap);
    UIImage *newImage = [UIImage imageWithCGImage:newImageRef];

    // Clean up
    CGContextRelease(bitmap);
    CGImageRelease(newImageRef);

    return newImage;
}

Esta é a licença desse arquivo:

// Created by Trevor Harmon on 8/5/09.
// Free for personal or commercial use, with or without modification.
// No warranty is expressed or implied.

Existe uma categoria UIImage extremamente eficiente chamada NYXImagesKit. Ele usa vDSP, CoreImage e vImage para ser o mais rápido possível. Tem uma categoria UIImage + Rotating que salvou meu dia :)

https://github.com/Nyx0uf/NYXImagesKit

Para Swift: Aqui está uma extensão simples para o UIImage:

//ImageRotation.swift

import UIKit

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: CGPointZero, size: size))
        let t = CGAffineTransformMakeRotation(degreesToRadians(degrees));
        rotatedViewBox.transform = t
        let rotatedSize = rotatedViewBox.frame.size

        // Create the bitmap context
        UIGraphicsBeginImageContext(rotatedSize)
        let bitmap = UIGraphicsGetCurrentContext()

        // 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
        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)
        }

        CGContextScaleCTM(bitmap, yFlip, -1.0)
        CGContextDrawImage(bitmap, CGRectMake(-size.width / 2, -size.height / 2, size.width, size.height), CGImage)

        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return newImage
    }
}

( Fonte )

Use-o com:

rotatedPhoto = rotatedPhoto?.imageRotatedByDegrees(90, flip: false) 

O primeiro irá girar uma imagem e inverter se a opção estiver definida como verdadeira.