为啥此裁剪代码会导致图像旋转？
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【中文标题】为啥此裁剪代码会导致图像旋转？【英文标题】：Why Does this Cropping Code Result in a Rotated Image?为什么此裁剪代码会导致图像旋转？ 【发布时间】：2012-10-08 14:48:28 【问题描述】：这个问题的标题应该很清楚。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。问题是图像一旦被裁剪，就会以与原始源图像不同的方向显示。这是为什么？我该怎么办？
-(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 cmets 表明问题的根本原因是删除了 EXIF 标记，我尝试使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。也许它会帮助某人为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.));
见https://***.com/a/5184134/549273
【问题讨论】：
我相信Apple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。 图片来自 iPhone 摄像头，所以它应该有一个 EXIF 标签。 在将 exif 数据绘制到上下文中时，您没有将其考虑在内。图像将始终处于其“原始”方向。 UIImage 根据 exif 旋转它。除了您将其原始绘制到没有 exif 数据的新 UIImage 中，因此“未旋转”。 有没有办法通过上下文保存EXIF数据？ 【参考方案1】：我认为您最好的选择是从传入的图像中获取方向，然后使用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"];
然后当你创建你的UIImage:
croppedImage = [UIImage imageWithCGImage:subImageRef
scale:1.0
orientation:[orientation intValue]];
希望这是你的起点，至少。
【讨论】：
【参考方案2】：你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 所以我不得不改变这个答案：
ios UIImagePickerController result image orientation after upload
但代码运行良好。请记住，它返回一个图像并且它没有编辑图像，我只是因为那个简单的错误而努力让它正确。顺便说一句，你不应该使用 UIImageOrientation 而是 UIImageOrientation.rawValue，至少在 swift 中是这样。
我将在此处留下 swift 的代码，希望它有所帮助：
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
【讨论】：
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