AVFoundation tap to focus feedback rectangle

Question

I am developing an iphone application where I directly use AVFoundation to capture videos via the camera.

I\'ve implemented a feature to enable the tap to focus

Answer 1

Adding to Anil's brilliant answer: Instead of doing the calculations yourself, you should have a look at AVCaptureVideoPreviewLayer's captureDevicePointOfInterestForPoint:. It will give you a much more consistent focus point (available from iOS 6 and forward).

- (void) focus:(CGPoint) aPoint;
{
    Class captureDeviceClass = NSClassFromString(@"AVCaptureDevice");
    if (captureDeviceClass != nil) {
        AVCaptureDevice *device = [captureDeviceClass defaultDeviceWithMediaType:AVMediaTypeVideo];
        if([device isFocusPointOfInterestSupported] &&
           [device isFocusModeSupported:AVCaptureFocusModeAutoFocus]) {

            CGPoint focusPoint = [self.captureVideoPreviewLayer captureDevicePointOfInterestForPoint:aPoint];
            if([device lockForConfiguration:nil]) {
                [device setFocusPointOfInterest:CGPointMake(focusPoint.x,focusPoint.y)];
                [device setFocusMode:AVCaptureFocusModeAutoFocus];
                if ([device isExposureModeSupported:AVCaptureExposureModeAutoExpose]){
                    [device setExposureMode:AVCaptureExposureModeAutoExpose];
                }
                [device unlockForConfiguration];
            }
        }
    }
}

The documentation is available here: https://developer.apple.com/library/ios/documentation/AVFoundation/Reference/AVCaptureVideoPreviewLayer_Class/index.html#//apple_ref/occ/instm/AVCaptureVideoPreviewLayer/captureDevicePointOfInterestForPoint: