为什么 UIPasteboard 忽略我使用的图像方向？

Question

我正在从相机中拍摄图像，并将其旋转到新的方向，然后将其粘贴到通用粘贴板上。但是，无论我向方向传递什么内容，稍后通过粘贴板粘贴命令粘贴的内容都会被定向，就好像它是 UIImageOrientationUp 一样。

    CGImageRef croppedImageRef = CGImageCreateWithImageInRect([self CGImage], CGRectMake(rect.origin.y, [self size].width - rect.origin.x - rect.size.width, rect.size.height, rect.size.width));
    UIImage *croppedImage = [UIImage imageWithCGImage:croppedImageRef scale:self.scale orientation:orientation];
    CGImageRelease(croppedImageRef);
    [[UIPasteboard generalPasteboard] setImage:croppedImage];   

我使用类似的代码成功旋转相机中的图像并将其插入相册中：

    CGImageRef croppedImageRef = CGImageCreateWithImageInRect([self CGImage], CGRectMake(rect.origin.y, [self size].width - rect.origin.x - rect.size.width, rect.size.height, rect.size.width));
    UIImage *croppedImage = [UIImage imageWithCGImage:croppedImageRef scale:self.scale orientation:orientation];
    CGImageRelease(croppedImageRef);
    [self writeUIImageToCameraRoll:croppedImage withOrientation:orientation];

为什么我无法按照粘贴板的要求旋转图像？粘贴操作是否使用 EXIF 方向？如果是这样，imageWithCGImage是否将原始EXIF复制到新图像？

Answer 1

我相信粘贴板更喜欢 PNG，它会去除附加到图像的任何 EXIF 数据。

NSLog( @"UIPasteboardTypeListImage: %@", UIPasteboardTypeListImage ); nets：

UIPasteboardTypeListImage: (
    "public.png",
    "public.tiff",
    "public.jpeg",
    "com.compuserve.gif"
)

解决方法是将 JPEG 数据保存到粘贴板：

NSData *jpegData = UIImageJPEGRepresentation(img, 1.0);
[[UIPasteboard generalPasteboard] setData:jpegData forPasteboardType:(id)kUTTypeJPEG];
...
NSData *pbImgData = [[UIPasteboard generalPasteboard] dataForPasteboardType:(id)kUTTypeJPEG];
UIImage *pbImg = [UIImage imageWithData:pbImgData];

或者从粘贴板获取图像后重置图像的方向:

[[UIPasteboard generalPasteboard] setImage:img];
...
UIImage *pbImg = [[UIPasteboard generalPasteboard] image];
UIImage *correctedImage = [UIImage imageWithCGImage:[pbImg CGImage] scale:pbImg.scale orientation:__whateverOrientationDesired];