Flipping Quicktime preview & capture

Question

I need to horizontally flip some video I'm previewing and capturing. A-la iChat, I have a webcam and want it to appear as though the user is looking in a mirror.

I'm previewing Quicktime video in a QTCaptureView. My capturing is done frame-by-frame (for reasons I won't get into) with something like:

imageRep = [NSCIImageRep imageRepWithCIImage: [CIImage imageWithCVImageBuffer: frame]];
image = [[NSImage alloc] initWithSize: [imageRep size]];
[image addRepresentation: imageRep];
[movie addImage: image forDuration: someDuration withAttributes: someAttributes];

Any tips?

Answer 1

You could do this by taking the CIImage you're getting from the capture and running it through a Core Image filter to flip the image around. You would then pass the resulting image into your image rep rather than the original one. The code would look something like:

CIImage* capturedImage = [CIImage imageWithCVImageBuffer:buffer];
NSAffineTransform* flipTransform = [NSAffineTransform transform];
CIFilter* flipFilter;
CIImage* flippedImage;

[flipTransform scaleByX:-1.0 y:1.0]; //horizontal flip
flipFilter = [CIImage filterWithName:@"CIAffineTransform"];
[flipFilter setValue:flipTransform forKey:@"inputTransform"];
[flipFilter setValue:capturedImage forKey:@"inputImage"];
flippedImage = [flipFilter valueForKey:@"outputImage"];
imageRep = [NSCIImageRep imageRepWithCIImage:flippedImage];
...

Answer 2

Nothing like resurrecting an old question. Anyway I came here and almost found what I was looking for thanks to Brian Webster but if anyone is looking for the wholesale solution try this after setting your class as the delegate of the QTCaptureView instance:

- (CIImage *)view:(QTCaptureView *)view willDisplayImage:(CIImage *)image {
//mirror image across y axis
return [image imageByApplyingTransform:CGAffineTransformMakeScale(-1, 1)];
}

Answer 3

Thanx alot for this QTKit/Core Video mirror filter code example. Saved my day!