How to Rotate a UIImage 90 degrees?

I believe the easiest way (and thread safe too) is to do:

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

Note: As Brainware said this only modifies the orientation data of the image - the pixel data is untouched. For some applications, this may not be enough.

Or in Swift:

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

Check out the simple and awesome code of Hardy Macia at: cutting-scaling-and-rotating-uiimages

Just call

UIImage *rotatedImage = [originalImage imageRotatedByDegrees:90.0];

Thanks Hardy Macia!

Header:

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

Since the link may die, here's the complete code

////  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;

What about something like:

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;}