UIImagePNGRepresentation问题？ /图像旋转了90度

我想从UIImagePickerController加载图像，然后将选定的照片保存到我的应用程序的文档目录。

UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage]; NSData *data1 = UIImagePNGRepresentation(image); NSString *fileName = "1.png"; NSString *path = //get Document path, then add fileName BOOL succ = [data1 writeToFile:path atomically:YES]; 

但是在将图像保存到我的文档后，我发现图像旋转了90度，然后将UIImagePNGRepresentation方法更改为UIImageJPEGRepresentation，这一次很好，谁知道这是什么问题？

Answer 1

我有同样的问题，只是找出原因：从iOS 4.0开始，当照相机拍照时它不会在保存之前旋转它，它只是在JPEG的EXIF数据中设置旋转标志。

如果将UIImage保存为JPEG，则会设置旋转标志。

PNG不支持旋转标志，因此如果将UIImage保存为PNG，则它将被错误地旋转，并且没有设置标志来修复它。 所以如果你想要PNG，你必须自己旋转它们。

我会称这是一个PNG保存function的错误，但这只是一个意见（他们至less应该警告你）。

Answer 2

我用下面的代码解决了这个问题。

 - (UIImage *)scaleAndRotateImage:(UIImage *)image { int kMaxResolution = 640; CGImageRef imgRef = image.CGImage; CGFloat width = CGImageGetWidth(imgRef); CGFloat height = CGImageGetHeight(imgRef); CGAffineTransform transform = CGAffineTransformIdentity; CGRect bounds = CGRectMake(0, 0, width, height); if (width > kMaxResolution || height > kMaxResolution) { CGFloat ratio = width/height; if (ratio > 1) { bounds.size.width = kMaxResolution; bounds.size.height = bounds.size.width / ratio; } else { bounds.size.height = kMaxResolution; bounds.size.width = bounds.size.height * ratio; } } CGFloat scaleRatio = bounds.size.width / width; CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef)); CGFloat boundHeight; UIImageOrientation orient = image.imageOrientation; switch(orient) { case UIImageOrientationUp: //EXIF = 1 transform = CGAffineTransformIdentity; break; case UIImageOrientationUpMirrored: //EXIF = 2 transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0); transform = CGAffineTransformScale(transform, -1.0, 1.0); break; case UIImageOrientationDown: //EXIF = 3 transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height); transform = CGAffineTransformRotate(transform, M_PI); break; case UIImageOrientationDownMirrored: //EXIF = 4 transform = CGAffineTransformMakeTranslation(0.0, imageSize.height); transform = CGAffineTransformScale(transform, 1.0, -1.0); break; case UIImageOrientationLeftMirrored: //EXIF = 5 boundHeight = bounds.size.height; bounds.size.height = bounds.size.width; bounds.size.width = boundHeight; transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width); transform = CGAffineTransformScale(transform, -1.0, 1.0); transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); break; case UIImageOrientationLeft: //EXIF = 6 boundHeight = bounds.size.height; bounds.size.height = bounds.size.width; bounds.size.width = boundHeight; transform = CGAffineTransformMakeTranslation(0.0, imageSize.width); transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0); break; case UIImageOrientationRightMirrored: //EXIF = 7 boundHeight = bounds.size.height; bounds.size.height = bounds.size.width; bounds.size.width = boundHeight; transform = CGAffineTransformMakeScale(-1.0, 1.0); transform = CGAffineTransformRotate(transform, M_PI / 2.0); break; case UIImageOrientationRight: //EXIF = 8 boundHeight = bounds.size.height; bounds.size.height = bounds.size.width; bounds.size.width = boundHeight; transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0); transform = CGAffineTransformRotate(transform, M_PI / 2.0); break; default: [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"]; } UIGraphicsBeginImageContext(bounds.size); CGContextRef context = UIGraphicsGetCurrentContext(); if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) { CGContextScaleCTM(context, -scaleRatio, scaleRatio); CGContextTranslateCTM(context, -height, 0); } else { CGContextScaleCTM(context, scaleRatio, -scaleRatio); CGContextTranslateCTM(context, 0, -height); } CGContextConcatCTM(context, transform); CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef); UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return imageCopy; } 

Answer 3

试试这个：

 func rotateImage(image: UIImage) -> UIImage { if (image.imageOrientation == UIImageOrientation.Up ) { return image } UIGraphicsBeginImageContext(image.size) image.drawInRect(CGRect(origin: CGPoint.zero, size: image.size)) let copy = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return copy } 

Answer 4

下面的swift函数解决了这个问题。

 var rotatedCopy: UIImage { if (imageOrientation == UIImageOrientation.Up) { return self } UIGraphicsBeginImageContext(size) drawInRect(CGRect(origin: CGPoint.zeroPoint, size: size)) let copy = UIGraphicsGetImageFromCurrentImageContext() UIGraphicsEndImageContext() return copy } 

是的，这很简单，只是因为drawInRect函数会考虑图像的方向。

Answer 5

我已经创build了这个UIImage扩展来解决这个问题，基于这个响应 UIImagePNGRepresentation。 所以我build议使用这个类func UIImage.PNGRepresentation(img: UIImage)而不是UIKit func UIImagePNGRepresentation。

Swift 3代码：

 // MyUIImage.swift // MyEasyMovie-Public-App // // Created by Ahmed Zahraz on 19/12/2016. // Copyright © 2016 AhmedZahraz. All rights reserved. import Foundation import UIKit extension UIImage { public class func PNGRepresentation(_ img: UIImage) -> Data? { // No-op if the orientation is already correct if (img.imageOrientation == UIImageOrientation.up) { return UIImagePNGRepresentation(img); } // 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. var transform:CGAffineTransform = CGAffineTransform.identity if (img.imageOrientation == UIImageOrientation.down || img.imageOrientation == UIImageOrientation.downMirrored) { transform = transform.translatedBy(x: img.size.width, y: img.size.height) transform = transform.rotated(by: CGFloat(M_PI)) } if (img.imageOrientation == UIImageOrientation.left || img.imageOrientation == UIImageOrientation.leftMirrored) { transform = transform.translatedBy(x: img.size.width, y: 0) transform = transform.rotated(by: CGFloat(M_PI_2)) } if (img.imageOrientation == UIImageOrientation.right || img.imageOrientation == UIImageOrientation.rightMirrored) { transform = transform.translatedBy(x: 0, y: img.size.height); transform = transform.rotated(by: CGFloat(-M_PI_2)); } if (img.imageOrientation == UIImageOrientation.upMirrored || img.imageOrientation == UIImageOrientation.downMirrored) { transform = transform.translatedBy(x: img.size.width, y: 0) transform = transform.scaledBy(x: -1, y: 1) } if (img.imageOrientation == UIImageOrientation.leftMirrored || img.imageOrientation == UIImageOrientation.rightMirrored) { transform = transform.translatedBy(x: img.size.height, y: 0); transform = transform.scaledBy(x: -1, y: 1); } // Now we draw the underlying CGImage into a new context, applying the transform // calculated above. let ctx:CGContext = CGContext(data: nil, width: Int(img.size.width), height: Int(img.size.height), bitsPerComponent: img.cgImage!.bitsPerComponent, bytesPerRow: 0, space: img.cgImage!.colorSpace!, bitmapInfo: img.cgImage!.bitmapInfo.rawValue)! ctx.concatenate(transform) if (img.imageOrientation == UIImageOrientation.left || img.imageOrientation == UIImageOrientation.leftMirrored || img.imageOrientation == UIImageOrientation.right || img.imageOrientation == UIImageOrientation.rightMirrored ) { ctx.draw(img.cgImage!, in: CGRect(x:0,y:0,width:img.size.height,height:img.size.width)) } else { ctx.draw(img.cgImage!, in: CGRect(x:0,y:0,width:img.size.width,height:img.size.height)) } // And now we just create a new UIImage from the drawing context let cgimg:CGImage = ctx.makeImage()! let imgEnd:UIImage = UIImage(cgImage: cgimg) return UIImagePNGRepresentation(imgEnd) } }