Capturing zoomed preview view in AVFoundation

Question

I am working with zoom functionality in AVFoundation camera, i have implemented zoom by scaling the view that has AVCaptureVideoPreviewLayer. Now i want to capture the zoomed image.

here is my code for adding AVFoundationVideoPreviewLayer to view:

 // create a uiview subclass for showing the camera feed
 UIView *previewView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 430)];
 [[self view] addSubview:previewView];

 CGRect layerRect = CGRectMake(0, 0, 320, 430);
 [[self avCaptureVideoPreviewLayer] setBounds:layerRect];

 [[self  previewLayer] setPosition:CGPointMake(CGRectGetMidX(layerRect), CGRectGetMidY(layerRect))];

 // add the video previewview layer to the preview view
 [[previewView layer] addSublayer:[self avCaptureVideoPreviewLayer]];

code for zooming preview view

  // zoom the preview view using core graphics
 [previewView setTransform:CGAffineTransformMakeScale(2.0, 2.0 )];

Now i want to capture this zoomed image from previewView

Thanks in advance.

Answer 1

Finally i have managed to add capturing zoomed photo in my app. Its a bit ugly but it works. I used UIImage+resize code from the net and then scaled the image to zoom scale, and the calculated the offset position for the zoomed region [that is visible in the camera view] and then i cropped it.

Now my app crashes sometimes when the zoom scale is at max i.e. at 6x. I am receiving memory problem as the zoomed image is too big, i will ask this as a another question.

Hoping this code might be usefull for someone.

 if (cameraZoom > 1.0) 
 {
        // save the images original size
        CGSize orgSize = [image size];  

        // resize the image to the zoom scale  
        image = [image resizedImage:CGSizeMake(image.size.width * cameraZoom, image.size.height *cameraZoom) interpolationQuality:kCGInterpolationNone];           

        // now calculate the offset x and offset y
        CGFloat offsetX = ( image.size.width / 2 ) - (orgSize.width /2) ;
        CGFloat offsetY =  ( image.size.height / 2 ) - (orgSize.height /2);

         // crop the image from the offset position to the original width and height
         image = [image croppedImage:CGRectMake(offsetX, offsetY, orgSize.width, orgSize.height)];
    }


    UIButton *imgBtn = (UIButton *)[self.view viewWithTag:500];
    [imgBtn setImage:image forState:UIControlStateNormal];