pinch zooming in image viewer - objective-c

Question

I have an UIImageView. I need pinch zoom.
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 90, 320, 38)];
[imageView setImage:[UIImage imageNamed:#"accesspanel.png"]];
[self.view addSubview: imageView];

Answer 1

You can add the imageview inside a scrollview and can use Scrollview delegate for the this purpose
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return self.imageView;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.scrollView.minimumZoomScale=0.5;
self.scrollView.maximumZoomScale=6.0;
self.scrollView.contentSize=CGSizeMake(1280, 960);
self.scrollView.delegate=self;
}

Answer 2

First ---> ADD Pinch Gesture to your Image View -:
UIPinchGestureRecognizer *pgr = [[UIPinchGestureRecognizer alloc]
initWithTarget:self action:#selector(handlePinchGesture:)];
pgr.delegate = self;
[imageView addGestureRecognizer:pgr];
Second ---> Implement Pinch Gesture -:
- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer {
if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
// Reset the last scale, necessary if there are multiple objects with different scales.
lastScale = [gestureRecognizer scale];
}
if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
[gestureRecognizer state] == UIGestureRecognizerStateChanged) {
CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:#"transform.scale"] floatValue];
// Constants to adjust the max/min values of zoom.
const CGFloat kMaxScale = 2.0;
const CGFloat kMinScale = 1.0;
CGFloat newScale = 1 - (lastScale - [gestureRecognizer scale]); // new scale is in the range (0-1)
newScale = MIN(newScale, kMaxScale / currentScale);
newScale = MAX(newScale, kMinScale / currentScale);
CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
[gestureRecognizer view].transform = transform;
lastScale = [gestureRecognizer scale]; // Store the previous. scale factor for the next pinch gesture call
}
}

Answer 3

UIPinchGestureRecognizer *pinchGestureRecognizer=[[UIPinchGestureRecognizer alloc]initWithTarget:self action:#selector(pinchGestureDetected:)];
[pinchGestureRecognizer setDelegate:self];
[_third_imageview addGestureRecognizer:pinchGestureRecognizer];
- (void)pinchGestureDetected:(UIPinchGestureRecognizer *)recognizer
{
UIGestureRecognizerState state = [recognizer state];
if (state == UIGestureRecognizerStateBegan || state ==UIGestureRecognizerStateChanged)
{
CGFloat scale = [recognizer scale];
[recognizer.view setTransform:CGAffineTransformScale(recognizer.view.transform, scale, scale)];
[recognizer setScale:1.0];
}
}