ios - Pinch/zoom from current scale

Question

The following code correctly pinches/zooms the container view, but only after it jumps to a scale of 1.0. How can I modify it so that the container view scales from it's current scale?

UIPinchGestureRecognizer *twoFingerPinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(twoFingerPinch:)];
[self.container addGestureRecognizer:twoFingerPinch];

- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer 
{
    _scale = recognizer.scale;
    CGAffineTransform tr = CGAffineTransformScale(self.view.transform, _scale, _scale);
    self.container.transform = tr;
}

Did you solve your problem? If yes then please share the code. — Manthan, Aug 27 '13 at 09:02

score 9 · Answer 1 · answered May 28 '12 at 07:14

In .h file, add:

CGFloat _lastScale;

In .m file,

- (id)init  {
    ...
    _lastScale = 1.0f;
    ...
}

- (void)twoFingerPinch:(UIPinchGestureRecognizer *)recognizer 
{
    if (recognizer.state == UIGestureRecognizerStateEnded)  {
        _lastScale = 1.0f;
        return;
    }

    CGFloat scale = 1.0f - (_lastScale - recognizer.scale);
    CGAffineTransform tr = CGAffineTransformScale(self.view.transform, scale, scale);
    self.container.transform = tr;

    _lastScale = recognizer.scale;
}

_lastScale and recognizer.scale are always pretty much the same, so scale is always very near 1.0, so the view just barely zooms in or out. — soleil, May 29 '12 at 04:32

score 2 · Answer 2 · answered Jan 24 '13 at 22:18

Here's how I do it:

- (void)handlePinchGesture:(UIPinchGestureRecognizer *)recognizer {

    static float initialDifference = 0.0;
    static float oldScale = 1.0;

    if (recognizer.state == UIGestureRecognizerStateBegan){
        initialDifference = oldScale - recognizer.scale;
    }

    CGFloat scale = oldScale - (oldScale - recognizer.scale) + initialDifference;

    myView.transform = CGAffineTransformScale(self.view.transform, scale, scale);

    oldScale = scale;    

}

This requires more coding to zoom out. – John Riselvato Apr 02 '13 at 18:25 — John Riselvato, Apr 02 '13 at 18:25

ios - Pinch/zoom from current scale

2 Answers2