UIImagePNGRepresentation問題？ /圖像旋轉90度

Question

我想從UIImagePickerController加載圖像，然後將選定的照片保存到我的應用程序的文檔目錄中。

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]; 

但之後，我將圖像保存到我的文檔，我發現，在圖像旋轉90度，然後我改變方法UIImagePNGRepresentation到UIImageJPEGRepresentation，這次是很好，誰知道是什麼問題？

Answer 1

我有同樣的問題，只是想出了原因：從iOS 4.0開始，當相機拍照時它不會在保存前旋轉它，它只是在JPEG的EXIF數據中設置旋轉標誌。

如果將UIImage保存爲JPEG，則會設置旋轉標誌。

PNG不支持旋轉標誌，因此如果將UIImage保存爲PNG，它將被錯誤地旋轉，並且沒有設置標誌來修復它。所以如果你想要PNG，你必須自己旋轉它們。

我會稱這是一個PNG保存功能的錯誤，但這只是一個意見（他們至少應該警告你）。

Answer 2

我用下面的代碼解決了這個問題。

- (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

下面的swift函數可以解決問題。

var rotatedCopy: UIImage { 
    if (imageOrientation == UIImageOrientation.Up) { 
     return self 
    } 

    UIGraphicsBeginImageContext(size) 

    drawInRect(CGRect(origin: CGPoint.zeroPoint, size: size)) 
    let copy = UIGraphicsGetImageFromCurrentImageContext() 

    UIGraphicsEndImageContext() 

    return copy 
} 

燁就是這麼簡單，只是因爲drawInRect功能將圖像的方向考慮。

Answer 4

試試這個：

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 5

我創造了這個擴展的UIImage來解決這個問題，UIImagePNGRepresentation，基於this response。所以我建議使用這個類func UIImage.PNGRepresentation(img: UIImage)而不是UIKit func UIImagePNGRepresentation。

夫特3代碼：

// 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) 
    } 

}