如何将 UIImage 旋转 90 度？

Posted 2023-03-11

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【中文标题】如何将 UIImage 旋转 90 度？【英文标题】：How to Rotate a UIImage 90 degrees? 【发布时间】：2009-08-22 05:48:29 【问题描述】：

我有一个UIImage 即UIImageOrientationUp（纵向），我想将其逆时针旋转 90 度（横向）。我不想使用CGAffineTransform。我希望UIImage 的像素实际移动位置。我正在使用一段代码（如下所示），最初旨在调整UIImage 的大小来执行此操作。我将目标大小设置为UIImage 的当前大小，但出现错误：

（错误）：CGBitmapContextCreate：无效数据字节/行：对于 8 个整数位/分量、3 个分量、kCGImageAlphaPremultipliedLast，应至少为 1708。

（当我提供一个较小的尺寸作为目标尺寸 BTW 时，我不会收到错误消息）。如何仅使用核心图形功能将UIImage 逆时针旋转 90 度，同时保留当前大小？

-(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;

【问题讨论】：

我找到了另一个有用的链接.. 希望这对某人有帮助.. mobiledevelopertips.com/user-interface/… 解决方案.......***.com/questions/5427656/… 我的问题是上传到 Amazon S3 的照片被旋转了。这个解决方案解决了视觉和上传的问题。 ***.com/questions/30701578/… hey nilam 看到这个后我会删除 【参考方案1】：

我相信最简单的方法（也是线程安全的）是：

//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];

注意：正如 Brainware 所说，这只修改了图像的方向数据 - 像素数据未受影响。对于某些应用程序，这可能还不够。

或者在 Swift 中：

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

【讨论】：

使其更通用：UIImage * origImg = [UIImage imageNamed:@"1.JPG"]; UIImage* fixed=[UIImage imageWithCGImage:[origImg CGImage] scale:1.0orientation:origImg.imageOrientation]; 这实际上并没有旋转图像。它复制图像并将图像的 imageFlags 属性的 imageOrientation 位设置为 0、1、2 或 3。某些类会忽略这些标志，例如 UIActivityViewController。如果您确实需要旋转图像，请参阅 Ben Groot 的回答，即 Hardy Macia 的 UIImage 扩展。如果您的应用同时在视网膜和非视网膜屏幕上使用，则将比例设置为 1.0 将不起作用，您必须获取 originalImage.scale 并将其作为比例组件传递。据我所知，似乎已停止在 ios10 中工作。 let img = UIImage(cgImage: myImage!.cgImage!, scale: UIScreen.main.scale, orientation: .right)【参考方案2】：

在 cutting-scaling-and-rotating-uiimages 上查看 Hardy Macia 的简单而出色的代码

只要打电话

UIImage *rotatedImage = [originalImage imageRotatedByDegrees:90.0];

感谢哈迪玛西亚！

标题：

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

由于链接可能失效，这里是完整的代码

//
//  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;

【讨论】：

...链接已失效。 +1 包含完整代码【参考方案3】：

类似的东西呢：

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;

【讨论】：

我的评论是 drawAtPoint 可能必须在调用后调用以设置正确的 RotateCTM。尝试将 drawAtPoint 移动到 UIGraphicsGetImageFromCurrentImageContext 之前这不适用于后台线程。 UIGraphicsGetCurrentContext() 不是线程安全的，只能在主 (UI) 线程上调用。对 CGContextRotateCTM() 的最后一次调用可能应该旋转 180，而不是 90。事实上，......向下可能应该旋转 180，而......向上可能不应该旋转。在 iOS 4 及更高版本中，您可以从应用程序的任何线程调用 UIGraphicsGetCurrentContext 函数。前后需要CGContextTranslateCTM(ctx, width/2, height/2)。【参考方案4】：

这看起来很奇怪，下面的代码为我解决了这个问题：

+ (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;

【讨论】：

它之所以有效，是因为在矩形中绘制后不会保留图像方向。是的，这将有助于从图像中删除方向函数名应该是removeOrientationProperty【参考方案5】：

线程安全的旋转函数如下（效果更好）：

-(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;

【讨论】：

您的代码有问题...它在UIImageOrientationDown 的图像周围添加了一个奇怪的白框。你不想调用 CGColorSpaceRelease(colorspace)，见***.com/questions/5269815/… 对那个版本很抱歉【参考方案6】：

我对上述所有问题都有疑问，包括批准的答案。我将 Hardy 的类别转换回一种方法，因为我想要的只是旋转图像。下面是代码和用法：

- (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;

及用法：

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

谢谢哈代！

【讨论】：

【参考方案7】：

将图像旋转 90 度（顺时针/逆时针方向）

函数调用 -

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

实施：

- (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;

【讨论】：

这会增加图片尺寸【参考方案8】：

这是一个 UIImage 的 Swift 扩展，它可以将图像旋转任意角度。像这样使用它：let rotatedImage = image.rotated(byDegrees: degree)。我在其他答案之一中使用了 Objective-C 代码，并删除了我们不正确的几行（旋转框的东西），并将其变成了 UIImage 的扩展。

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

【讨论】：

效果很好！我对其进行了一些更改，以便可以交换宽度和高度： func rotate(byDegrees degree: Double, toSize: CGSize? = nil) -> UIImage let rotateSize = toSize ?? self.size 这不会正确设置图像的边界。您最终会得到一个超出原始边界的旋转图像。非常感谢。令人惊讶的是我今天花了多少时间在这上面。【参考方案9】：

如果您想添加一个照片旋转按钮，该按钮将继续以 90 度为增量旋转照片，请执行此操作。（finalImage 是一个已经在别处创建的 UIImage。）

- (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;

【讨论】：

【参考方案10】：

简单。只需更改图像方向标志即可。

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];

【讨论】：

【参考方案11】：

Swift 3 UIImage 扩展：

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()!)

【讨论】：

【参考方案12】：

Swift 4.2 版本的RawMean's answer：

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!

【讨论】：

气球增加了图像的重量。我的测试：旋转前 =============================== 宽度 3024.0 高度 3024.0 大小 4952213 字节 ======= ======================= 旋转后========================= ===== 宽度 3024.0 高度 3024.0 大小 35191195 字节 ============================== 巴里是对的，这个方法改变了图像的权重。【参考方案13】：

我尝试了这段代码，它工作正常，取自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;

【讨论】：

【参考方案14】：

对基于 Hardy Macia 代码的其他答案进行了微小更改。无需简单地创建整个UIView 对象来计算旋转图像的边界矩形。只需使用 CGRectApplyAffineTransform 对图像矩形应用旋转变换即可。

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;

【讨论】：

【参考方案15】：

“tint uiimage grayscale”似乎是适合这个的 Google-Fu

我马上就明白了：

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

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

How would I tint an image programmatically on the iPhone?

【讨论】：

【参考方案16】：

我喜欢Peter Sarnowski 的简单优雅的回答，但是当您不能依赖EXIF 元数据等时，它可能会导致问题。在您需要旋转实际图像数据的情况下，我建议您这样做：

- (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;

上面的代码获取一个方向为Landscape的图像（不记得是Landscape Left还是Landscape Right）并将其旋转为Portrait。这是一个可以根据您的需要进行修改的示例。

您必须使用的关键参数是CGContextRotateCTM(context, M_PI_2)，您可以在其中决定要旋转多少，但是您必须确保使用CGContextTranslateCTM(context, 0, -640) 仍然在屏幕上绘制图片。最后一部分对于确保您看到图像而不是空白屏幕非常重要。

欲了解更多信息，请查看source。

【讨论】：

对断开的链接投反对票，并且没有解释 -640 幻数。修复后会反转。【参考方案17】：

resize-a-uiimage-the-right-way 解释了许多代码示例中的一些问题，并且有一些代码 sn-ps 来帮助处理 UIImages - UIImage+resize.m 中的私有帮助器方法接受转换以允许旋转，所以您只需要将其公开为公共接口。

// 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;

这是来自该文件的许可证：

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

【讨论】：

【参考方案18】：

有一个非常高效的 UIImage 类别，名为 NYXImagesKit。它使用 vDSP、CoreImage 和 vImage 尽可能快。它有一个 UIImage+Rotating 类别拯救了我的一天:)

https://github.com/Nyx0uf/NYXImagesKit

【讨论】：

【参考方案19】：

对于 Swift：这是 UIImage 的一个简单扩展：

//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

(Source)

使用它：

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

如果flip设置为true，前者将旋转图像并翻转它。

【讨论】：

你能解释一下吗？由于某种原因，这似乎与纵横比混淆

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