imageOrientation 返回向上，但照片显示颠倒

Posted 2023-03-12

【中文标题】imageOrientation 返回向上，但照片显示颠倒

【英文标题】：imageOrientation returns Up, but photo shows up upsidedown

【发布时间】：2012-03-18 03:05:00

【问题描述】：

我正在从 iPad 照片库中抓取一些照片。我在横向模式下拍了几张测试照片，左侧是 iPad 主页按钮，然后是右侧。

所以在我的应用中，出于某种原因，有些照片是上下颠倒的。我检查了他们的imageOrientation 属性，它们都是0（意味着它们是UIImageOrientationUp）。所以这意味着我什至不知道我需要旋转哪些照片。

发生了什么，我如何判断哪些照片需要旋转？谢谢

【问题讨论】：

看到这个github.com/cosnovae/fixUIImageOrientation

你也可以参考类似的帖子AVFoundation Image orientation off by 90 degrees in the preview but fine in Camera roll

【参考方案1】：

一个 UIImage 有一个属性 imageOrientation，它指示 UIImageView 和其他 UIImage 消费者旋转原始图像数据。这个标志很有可能被保存到上传的 jpeg 图像中的 exif 数据中，但是您用来查看它的程序不支持该标志。

要在上传时旋转 UIImage 以正确显示，您可以使用如下类别： 在.h文件中

UIImagefixOrientation.h

@interface UIImage (fixOrientation)

- (UIImage *)fixOrientation;

@end

UIImagefixOrientation.m

@implementation UIImage (fixOrientation)

- (UIImage *)fixOrientation 

    // No-op if the orientation is already correct
    if (self.imageOrientation == UIImageOrientationUp) return self;

   // 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.
  CGAffineTransform transform = CGAffineTransformIdentity;

  switch (self.imageOrientation) 
      case UIImageOrientationDown:
      case UIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height);
         transform = CGAffineTransformRotate(transform, M_PI);
          break;

    case UIImageOrientationLeft:
    case UIImageOrientationLeftMirrored:
        transform = CGAffineTransformTranslate(transform, self.size.width, 0);
        transform = CGAffineTransformRotate(transform, M_PI_2);
        break;

    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform, 0, self.size.height);
        transform = CGAffineTransformRotate(transform, -M_PI_2);
        break;


switch (self.imageOrientation) 
    case UIImageOrientationUpMirrored:
    case UIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform, self.size.width, 0);
        transform = CGAffineTransformScale(transform, -1, 1);
        break;

    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform, self.size.height, 0);
        transform = CGAffineTransformScale(transform, -1, 1);
        break;


// Now we draw the underlying CGImage into a new context, applying the transform
// calculated above.
CGContextRef ctx = CGBitmapContextCreate(NULL, self.size.width, self.size.height,
                                         CGImageGetBitsPerComponent(self.CGImage), 0,
                                         CGImageGetColorSpace(self.CGImage),
                                         CGImageGetBitmapInfo(self.CGImage));
CGContextConcatCTM(ctx, transform);
switch (self.imageOrientation) 
    case UIImageOrientationLeft:
    case UIImageOrientationLeftMirrored:
    case UIImageOrientationRight:
    case UIImageOrientationRightMirrored:
        // Grr...
        CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width), self.CGImage);
        break;

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


// And now we just create a new UIImage from the drawing context
CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
UIImage *img = [UIImage imageWithCGImage:cgimg];
CGContextRelease(ctx);
CGImageRelease(cgimg);
return img;


@end

并在捕获图像保存或从图库中选择图像期间调用此函数。

【讨论】：

您好，感谢您的支持。但是，一个潜在的问题是颠倒的文件都返回 UIImageOrientationUp。它们都不返回 0 以外的任何值，这是有问题的。

你能把代码发给我吗？我会从我这边试试。我解决你的错误。

【参考方案2】：

没有进入你的图像代码，可能是由于 ios 上的翻转坐标系？

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CocoaDrawingGuide/Transforms/Transforms.html

~截图：

将视图配置为使用翻转坐标

实现翻转坐标所需的第一步是确定视图的默认方向。如果您更喜欢使用翻转坐标，有两种方法可以在绘制之前配置视图的坐标系：

覆盖视图的 isFlipped 方法并返回 YES。应用翻转 在渲染之前立即转换为您的内容。

因此，在您看来，您可以尝试添加 -(BOOL)isFlipped 并返回 YES 并测试是否有任何不同。

【参考方案3】：

我也面临同样的问题。使用这个函数来解决：

- (UIImage *)scaleAndRotateImage:(UIImage *) image 
int kMaxResolution = 320;

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;