Iphone 为什么此裁剪代码会导致旋转图像？

这个问题的标题应该相当清楚。下面的代码执行裁剪操作，然后在图像视图中显示新裁剪的照片。问题在于，图像一旦被裁剪，就会以与原始源图像不同的方向显示。为什么呢？我该怎么办呢

-(void)imagePickerController:(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
[self.popoverController dismissPopoverAnimated:true];

NSString *mediaType = [info
                       objectForKey:UIImagePickerControllerMediaType];
[self dismissModalViewControllerAnimated:YES];
if ([mediaType isEqualToString:(NSString *)kUTTypeImage]) {
    UIImage *image = [info
                      objectForKey:UIImagePickerControllerOriginalImage];


    CGRect rect = CGRectMake(0, ((image.size.height - image.size.width) / 2), image.size.width, image.size.width);


    CGImageRef subImageRef = CGImageCreateWithImageInRect(image.CGImage, rect);
    CGRect smallBounds = CGRectMake(rect.origin.x, rect.origin.y, CGImageGetWidth(subImageRef), CGImageGetHeight(subImageRef));

    UIGraphicsBeginImageContext(smallBounds.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextDrawImage(context, smallBounds, subImageRef);
    croppedImage = [UIImage imageWithCGImage:subImageRef];
    UIGraphicsEndImageContext();

    imageView.image = croppedImage;

*编辑

根据指出问题的根本原因是删除EXIF标记的评论，我尝试用以下代码更正方向。这仍然不能解决问题，但我认为这是朝着正确方向迈出的一步。也许它会帮助某人对这个问题提出一个新的答案

if (image.imageOrientation == UIImageOrientationLeft) {
        NSLog(@"left");
        CGContextRotateCTM (context, radians(90));

    } else if (image.imageOrientation == UIImageOrientationRight) {
        NSLog(@"right");
        CGContextRotateCTM (context, radians(-90));

    } else if (image.imageOrientation == UIImageOrientationUp) {
        NSLog(@"up");
        // NOTHING
    } else if (image.imageOrientation == UIImageOrientationDown) {
        NSLog(@"down");
        CGContextRotateCTM (context, radians(-180.));
    }

---

请参见

我认为您最好的选择是从传入图像中获取方向，然后通过适当的旋转创建新图像

从传入的信息字典中获取元数据：

NSDictionary *metadata = [info objectForKey:UIImagePickerControllerMediaMetadata];
NSNumber *orientation = [metadata objectForKey:@"Orientation"];

然后，当您创建

UIImage

时：

croppedImage = [UIImage imageWithCGImage:subImageRef 
                                   scale:1.0 
                             orientation:[orientation intValue]];

---

希望这至少是您的一个起点。

您应该做的是在处理之前修复图像方向，我遇到了同样的问题，我正在使用swift，因此我必须更改此答案：

但是代码工作得很好。请记住，它返回一个图像，而它没有编辑图像，我只是因为那个简单的错误而努力使它正确。顺便说一下，您不应该使用UIImageOrientation，而应该使用UIImageOrientation.rawValue，至少在swift中是这样

我将把swift的代码留在这里，希望能有所帮助：

extension UIImage {
public func fixOrientation() -> UIImage?{

    if self.imageOrientation.rawValue == UIImageOrientation.Up.rawValue {
        return self
    }

    var transform : CGAffineTransform = CGAffineTransformIdentity

    switch self.imageOrientation.rawValue {

    case UIImageOrientation.Down.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI))
    case UIImageOrientation.DownMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI))

    case UIImageOrientation.Left.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI_2))
    case UIImageOrientation.LeftMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI_2))

    case UIImageOrientation.Right.rawValue:
            print("working on right orientation")
            transform = CGAffineTransformTranslate(transform, 0, self.size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(-M_PI_2))
    case UIImageOrientation.RightMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, 0, self.size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(-M_PI_2))

    case UIImageOrientation.Up.rawValue: break
    case UIImageOrientation.UpMirrored.rawValue: break

    default: break
    }

    switch self.imageOrientation.rawValue {

    case UIImageOrientation.UpMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0)
            transform = CGAffineTransformScale(transform, -1, 1)
    case UIImageOrientation.DownMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.width, 0)
            transform = CGAffineTransformScale(transform, -1, 1)

    case UIImageOrientation.LeftMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.height, 0)
            transform = CGAffineTransformScale(transform, -1, 1)
    case UIImageOrientation.RightMirrored.rawValue:
            transform = CGAffineTransformTranslate(transform, self.size.height, 0)
            transform = CGAffineTransformScale(transform, -1, 1)

    case UIImageOrientation.Up.rawValue: break
    case UIImageOrientation.Down.rawValue: break
    case UIImageOrientation.Left.rawValue: break
    case UIImageOrientation.Right.rawValue: break

    default: break
    }

    let bitmapInfo = CGImageGetBitmapInfo(self.CGImage)

    let ctx = CGBitmapContextCreate(nil, Int(self.size.width), Int(self.size.height), CGImageGetBitsPerComponent(self.CGImage), 0, CGImageGetColorSpace(self.CGImage),
        bitmapInfo.rawValue)

    CGContextConcatCTM(ctx, transform)

    switch self.imageOrientation {

    case UIImageOrientation.Left:
            CGContextDrawImage(ctx, CGRectMake(0, 0, self.size.height, self.size.width), self.CGImage)
    case UIImageOrientation.LeftMirrored:
            CGContextDrawImage(ctx, CGRectMake(0, 0, self.size.height, self.size.width), self.CGImage)
    case UIImageOrientation.Right:
            CGContextDrawImage(ctx, CGRectMake(0, 0, self.size.height, self.size.width), self.CGImage)
    case UIImageOrientation.RightMirrored:
            CGContextDrawImage(ctx, CGRectMake(0, 0, self.size.height, self.size.width), self.CGImage)

    default:
        CGContextDrawImage(ctx, CGRectMake(0, 0, self.size.width, self.size.height), self.CGImage)

    }

    let cgimg = CGBitmapContextCreateImage(ctx)
    let image = UIImage(CGImage: cgimg!)

    return image

    }
}

---

我相信苹果使用EXIF标签来实现照片的旋转。您的新图像可能缺少该方向信息，因此显示不正确。该图像来自iPhone摄像头，因此应该有EXIF标记。在将其绘制到上下文中时，您没有考虑EXIF数据。图像将始终处于“原始”方向。UIImage根据exif旋转它。除了将其原始绘制到一个没有exif数据的新UIImage中以及“未旋转”之外。是否有任何方法通过上下文保留exif数据？