问如何将UIImage旋转90度？
EN

Stack Overflow用户

提问于 2009-08-22 05:48:30

回答 19查看 186.2K关注 0票数 183

我有一个UIImage是UIImageOrientationUp (肖像)，我想逆时针旋转90度(到风景)。我不想使用CGAffineTransform。我想让UIImage的像素真正地移动位置。我使用了一段代码(如下所示)，最初的目的是调整UIImage的大小来实现这一点。我将目标大小设置为UIImage的当前大小，但得到一个错误：

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

(每当我提供一个较小的大小作为目标大小BTW时，我都不会收到错误)。如何使用核心图形功能将我的UIImage旋转90度，同时保持当前大小？

-(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; 
}

ios

objective-c

uiimage

uikit

core-graphics

回答 19

Stack Overflow用户

回答已采纳

发布于 2009-08-22 22:20:05

像这样的东西怎么样：

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;
}

票数 90

Stack Overflow用户

发布于 2011-10-11 13:42:05

我认为最简单的方法(也是线程安全的)是这样做：

//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，这只会修改图像的方向数据-像素数据不会改变。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)

票数 420

Stack Overflow用户

发布于 2011-05-30 21:00:25

查看Hardy Macia的简单而令人惊叹的代码：cutting-scaling-and-rotating-uiimages

只要打个电话

UIImage *rotatedImage = [originalImage imageRotatedByDegrees:90.0];

谢谢Hardy Macia！

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;**

由于链接可能会死掉，下面是完整的代码

//
//  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;

票数 112

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/1315251

复制

相似问题

问如何将UIImage旋转90度？
EN

回答 19

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将UIImage旋转90度？EN

回答 19

Stack Overflow用户

Stack Overflow用户

Stack Overflow用户

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问如何将UIImage旋转90度？
EN