AVCaptureDevice Camera Zoom

Question

I have a simple AVCaptureSession running to get a camera feed in my app and take photos. How can I implement the \'pinch to zoom\' functionality using a UIGestureRecognize

Answer 1

Since iOS 7 you can set the zoom directly with the videoZoomFactor property of AVCaptureDevice.

Tie the scale property of the UIPinchGestureRecognizer to thevideoZoomFactor with a scaling constant. This will let you vary the sensitivity to taste:

-(void) handlePinchToZoomRecognizer:(UIPinchGestureRecognizer*)pinchRecognizer {
    const CGFloat pinchZoomScaleFactor = 2.0;

    if (pinchRecognizer.state == UIGestureRecognizerStateChanged) {
        NSError *error = nil;
        if ([videoDevice lockForConfiguration:&error]) {
            videoDevice.videoZoomFactor = 1.0 + pinchRecognizer.scale * pinchZoomScaleFactor;
            [videoDevice unlockForConfiguration];
        } else {
            NSLog(@"error: %@", error);
        }
    }
}

Note that AVCaptureDevice, along everything else related to AVCaptureSession, is not thread safe. So you probably don't want to do this from the main queue.