How to correctly orient image generated from AVCaptureVideoDataOutputSampleBufferDelegate

问题

I'm using AVCaptureVideoDataOutputSampleBufferDelegate and I receive a CMSampleBufferRef wich I convert to a UIImage - but the resulting image isn't correctly oriented.

// Get a CMSampleBuffer's Core Video image buffer for the media data
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0); 

// Get the number of bytes per row for the pixel buffer
void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 

// Get the number of bytes per row for the pixel buffer
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
// Get the pixel buffer width and height
size_t width = CVPixelBufferGetWidth(imageBuffer); 
size_t height = CVPixelBufferGetHeight(imageBuffer); 

// Create a device-dependent RGB color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

// Create a bitmap graphics context with the sample buffer data
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context); 
// Unlock the pixel buffer
CVPixelBufferUnlockBaseAddress(imageBuffer,0);

// Free up the context and color space
CGContextRelease(context); 
CGColorSpaceRelease(colorSpace);

// Create an image object from the Quartz image
UIImage *img = [UIImage imageWithCGImage:quartzImage];

// Release the Quartz image
CGImageRelease(quartzImage);

If I hold the iPhone in portrait mode the resulting image is rotated 90 degrees (anti-clockwise). If I hold the iPhone in landscape left orientation (home button is on the left) the resulting image is up. If I hold the iPhone in landscape right orientation (home button is on the right) the resulting image is upside-down.

I'm using the front camera of the device - but I will also be using the front camera, so the resulting image should always have the correct orientation.

来源：https://stackoverflow.com/questions/11246726/how-to-correctly-orient-image-generated-from-avcapturevideodataoutputsamplebuffe