根据UIImage的方向信息旋转图片

UIImage+Orientation.h

#import <UIKit/UIKit.h>

@interface UIImage (Orientation)

- (UIImage *)fixOrientation;

@end

UIImage+Orientation.m

#import "UIImage+Orientation.h"

@implementation UIImage (Orientation)

- (UIImage *)fixOrientation {
    UIImage *aImage = self;
    if (aImage==nil || !aImage) {
        return nil;
    }
    // No-op if the orientation is already correct
    if (aImage.imageOrientation == UIImageOrientationUp) return aImage;
    // 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.
    CGAffineTransform transform = CGAffineTransformIdentity;
    UIImageOrientation orientation=aImage.imageOrientation;
    int orientation_=orientation;
    switch (orientation_) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
    }
    switch (orientation_) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);
            
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
            
    }
    
    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    CGContextRef ctx = CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
                                             
                                             CGImageGetBitsPerComponent(aImage.CGImage), 0,
                                             
                                             CGImageGetColorSpace(aImage.CGImage),
                                             
                                             CGImageGetBitmapInfo(aImage.CGImage));
    
    CGContextConcatCTM(ctx, transform);
    switch (aImage.imageOrientation) {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            // Grr...
            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
            break;
        default:
            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
            break;
            
    }
    
    // And now we just create a new UIImage from the drawing context
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    
    aImage=img;
    img=nil;
    return aImage;
}

@end