相机图像方向答案

【问题标题】：Camera image orientation相机图像方向
【发布时间】：2011-04-15 19:33:26
【问题描述】：

在我的应用中，我使用相机拍摄图像。这些作为 NSData 表示形式存储在 NSArray 中。当我将 NSData 转换回图像时，方向现在是横向而不是纵向。

    NSData *data = UIImagePNGRepresentation([arrayImage objectAtIndex:0]);
    UIImage *tmp = [UIImage imageWithData:data];

有人解释一下吗？谢谢。

【问题讨论】：

标签： ios uiimage nsdata

【解决方案1】：

您应该修复相机捕获的图像的方向，代码如下，默认情况下，相机图像的方向不正确

- (UIImage *)fixrotation:(UIImage *)image
{

    if (image.imageOrientation == UIImageOrientationUp) return image;
    CGAffineTransform transform = CGAffineTransformIdentity;

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

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

        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, image.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationUpMirrored:
            break;
    }

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

        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.height, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationDown:
        case UIImageOrientationLeft:
        case UIImageOrientationRight:
            break;
    }

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

        default:
            CGContextDrawImage(ctx, CGRectMake(0,0,image.size.width,image.size.height), image.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;
}

【讨论】：

方向正确。不正确的是一些开发者在传输或显示图像时不尊重元数据的逻辑。

【解决方案2】：

我认为这是 SDK 的一个错误。我遇到了这个确切的问题，然后切换到 UIImageJPEGRepresentation 解决了这个问题。

【讨论】：

对此有任何确认吗？我遇到了同样的问题，无法为我的生活找到解决方法。使用 JPEG 表示对我来说是不可能的，因为我需要 alpha 通道 PNG 提供。
这对我有帮助。我已确认 JPEG 转换不会出现图像方向问题

【解决方案3】：

-[UIImage imageOrientation] 可能会有所帮助:)

图像方向会影响图像数据在绘制时的显示方式。默认情况下，图像以“向上”方向显示。但是，如果图像具有关联的元数据（例如 EXIF 信息），则此属性包含该元数据指示的方向。有关此属性的可能值列表，请参阅“UIImageOrientation”。

由于该属性是只读的，并且取决于您想要做什么，一个可能的（但丑陋的）解决方案可能是：

UIImage *sourceImage = [arrayImage objectAtIndex:0];
NSData *data = UIImagePNGRepresentation(sourceImage);
UIImage *tmp = [UIImage imageWithData:data];
UIImage *fixed = [UIImage imageWithCGImage:tmp.CGImage
                                     scale:sourceImage.scale
                               orientation:sourceImage.imageOrientation];

（未经测试，可能/必须有更清洁的东西）

编辑：第一部分是对您问题的回答，解释不仅仅是一个修复。

This 和 this （旧的？） 博客文章可能是您感兴趣的阅读材料。奇怪的是，当我使用UIImageJPEGRepresentation 将图像发送到服务器时，我从未遇到过这个问题......你正在使用哪个 iOS 版本？那可能是旧的 SDK 错误？

【讨论】：

这确实解决了应用程序内部的问题。但是，我在应用程序中以哪种方式定位图像并不重要，当我转换回 NSData 以通过电子邮件发送图像时，图像会从原始图像回到逆时针 90 度。这肯定看起来像一个错误？
编辑的答案带有有趣的链接，下次请发布更详细的问题。

【解决方案4】：

dispatch_async([self sessionQueue], ^{
        // Update the orientation on the still image output video connection before capturing.
        [[[self stillImageOutput] connectionWithMediaType:AVMediaTypeVideo] setVideoOrientation:[[(AVCaptureVideoPreviewLayer *)[[self previewView] layer] connection] videoOrientation]];

        // Flash set to Auto for Still Capture
        [AVCamViewController setFlashMode:AVCaptureFlashModeAuto forDevice:[[self videoDeviceInput] device]];

        // Capture a still image.
        [[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:[[self stillImageOutput] connectionWithMediaType:AVMediaTypeVideo] completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {

            if (imageDataSampleBuffer)
            {
                NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                UIImage *image = [[UIImage alloc] initWithData:imageData];
                [[[ALAssetsLibrary alloc] init] writeImageToSavedPhotosAlbum:[image CGImage] orientation:(ALAssetOrientation)[image imageOrientation] completionBlock:nil];
            }
        }];
    });

https://developer.apple.com/library/content/samplecode/AVCam/Introduction/Intro.html

【讨论】：

这解决了我在 iOS 14 上的问题。在 Swift 中如下：dataOutput.connection(with: .video)!.videoOrientation = self.previewLayer.connection!.videoOrientation

【解决方案5】：

//iOS Swift 3

func fixRotation(image: UIImage) -> UIImage
    {
        if (image.imageOrientation == .up)
        {
            return image
        }

        var transform: CGAffineTransform = .identity

        switch image.imageOrientation {
        case .down, .downMirrored:
            transform = transform.translatedBy(x: image.size.width, y: image.size.height)
            transform = transform.rotated(by: .pi)
        case .left, .leftMirrored:
            transform = transform.translatedBy(x: image.size.width, y: 0)
            transform = transform.rotated(by: .pi / 2)
        case .right, .rightMirrored:
            transform = transform.translatedBy(x: 0, y: image.size.height)
            transform = transform.rotated(by: -(.pi / 2))
        case .up, .upMirrored:
            break
        }

        switch image.imageOrientation {
        case .upMirrored, .downMirrored:
            transform = transform.translatedBy(x: image.size.width, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x: image.size.height, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        case .up, .down, .left, .right:
            break
        }

        // Now we draw the underlying CGImage into a new context, applying the transform
        // calculated above.

        let cgimage = image.cgImage
        let bitsPerComponent = cgimage?.bitsPerComponent
        let colorSpace = cgimage?.colorSpace
        let bitmapInfo = cgimage?.bitmapInfo

        let ctx = CGContext(data: nil, width: Int(image.size.width), height: Int(image.size.height), bitsPerComponent: bitsPerComponent! , bytesPerRow: 0, space: colorSpace!, bitmapInfo: bitmapInfo!.rawValue)

        ctx?.concatenate(transform)

        switch image.imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            // Grr...
            ctx?.draw(image.cgImage!, in: CGRect(x: 0, y: 0, width: image.size.height, height: image.size.width))
        default:
            ctx?.draw(image.cgImage!, in: CGRect(x: 0, y: 0, width: image.size.width, height: image.size.height))
        }

        let cgimg: CGImage = ctx!.makeImage()!
        let img = UIImage(cgImage: cgimg)
        return img
    }

【讨论】：

【解决方案6】：

这里是一个稍作修改的 Xamarin.iOS (C#) 版本的最佳答案，这样您也不必手动重写它；-)。

public static UIImage FixCameraImageRotation(UIImage image)
{
    if (image.Orientation == UIImageOrientation.Up) return image;

    var transform = CGAffineTransform.MakeIdentity();

    //handle orientation
    switch (image.Orientation)
    {
        case UIImageOrientation.Down:
        case UIImageOrientation.DownMirrored:
            transform.Rotate((float)Math.PI);
            transform.Translate(image.Size.Width, image.Size.Height);
            break;
        case UIImageOrientation.Left:
        case UIImageOrientation.LeftMirrored:
            transform.Rotate((float)Math.PI / 2);
            transform.Translate(image.Size.Width, 0);
            break;
        case UIImageOrientation.Right:
        case UIImageOrientation.RightMirrored:
            transform.Rotate(-(float)Math.PI / 2);
            transform.Translate(0, image.Size.Height);
            break;
    }

    //handle mirroring
    switch (image.Orientation)
    {
        case UIImageOrientation.UpMirrored:
        case UIImageOrientation.DownMirrored:
            transform.Translate(image.Size.Width, 0);
            transform.Scale(-1, 1);
            break;
        case UIImageOrientation.LeftMirrored:
        case UIImageOrientation.RightMirrored:
            transform.Translate(image.Size.Height, 0);
            transform.Scale(-1, 1);
            break;
    }

    //create context and apply transformation
    using (var context = new CGBitmapContext(
        IntPtr.Zero,
        (nint)image.Size.Width,
        (nint)image.Size.Height,
        image.CGImage.BitsPerComponent,
        image.CGImage.BytesPerRow,
        image.CGImage.ColorSpace,
        image.CGImage.BitmapInfo))
    {
        context.ConcatCTM(transform);

        //draw image
        switch (image.Orientation)
        {
            case UIImageOrientation.Left:
            case UIImageOrientation.LeftMirrored:
            case UIImageOrientation.Right:
            case UIImageOrientation.RightMirrored:
                context.DrawImage(new CGRect(0, 0, image.Size.Height, image.Size.Width), image.CGImage);
                break;
            default:
                context.DrawImage(new CGRect(0, 0, image.Size.Width, image.Size.Height), image.CGImage);
                break;
        }

        //convert result to UIImage
        using (var cgImage = context.ToImage())
        {
            var result = UIImage.FromImage(cgImage);
            return result;
        }
    }
}

【讨论】：