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objective-ccocoaquicktime

Flipping Quicktime preview & capture

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?

Solution

  • 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];
...