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copied!<p>This sample uses regular zooming capabilities of UIScrollView, which contains UIImageView as subview. You can find the implementation of such zooming in MWPhotoBrowser library for example. _imageView, _doubleTapBeganPoint, _longPressBeganPoint, _minScale are your class (UIScrollView subclass) iVars. So begin with initialization:</p> <pre><code>UILongPressGestureRecognizer* lpgs = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(imageLongPressed:)]; lpgs.minimumPressDuration = .2; [self addGestureRecognizer:lpgs]; </code></pre> <p>Standard zoom handler:</p> <pre><code>- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView { return _imageView; } </code></pre> <p>Using touchesBegan to catch double tap (UITapGestureRecognizer doesn't want to work with UILongPressGestureRecognizer in some reason):</p> <pre><code>- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [touches anyObject]; NSUInteger tapCount = touch.tapCount; switch (tapCount) { case 2: [self handleDoubleTapBegan:[touch locationInView:self.superview]]; break; default: break; } [[self nextResponder] touchesEnded:touches withEvent:event]; } - (void)handleDoubleTapBegan:(CGPoint)touchPoint { _doubleTapBeganPoint = touchPoint; NSLog(@"image double tap began at location: %@", NSStringFromCGPoint(touchPoint)); } </code></pre> <p>Handle long press and using difference in Y coordinates to calculate zoom scale. _minScale stores your initial zoomScale so we can restore it.</p> <pre><code>- (void) imageLongPressed:(UIGestureRecognizer*)gesture { if (gesture.state == UIGestureRecognizerStateBegan) { self.maximumZoomScale = _maxScale * 2; self.minimumZoomScale = _minScale / 3; _longPressBeganPoint = [gesture locationInView:self.superview]; [self setZoomScale:_minScale animated:YES]; NSLog(@"image long press began at location: %@", NSStringFromCGPoint(_longPressBeganPoint)); } else if (gesture.state == UIGestureRecognizerStateChanged) { CGPoint p = [gesture locationInView:self.superview]; //NSLog(@"image long press changed at location: %@", NSStringFromCGPoint(p)); if (CGPointEqualToPoint(_longPressBeganPoint, _doubleTapBeganPoint)) { _zoom = _minScale + (p.y - _longPressBeganPoint.y) / 100.0; NSLog(@"zoom scale: %f", _zoom); [self setZoomScale:_zoom animated:NO]; } } else if (gesture.state == UIGestureRecognizerStateEnded) { NSLog(@"image long press ended at location: %@", NSStringFromCGPoint([gesture locationInView:gesture.view])); if (self.zoomScale < _minScale) { [self setZoomScale:_minScale animated:YES]; NSLog(@"min zoom scale: %f", _minScale); } } } </code></pre>

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