Get curret size of UIImageView - objective-c

Question

I create a double layer with a UIImageView one on bottom and one overlay with this method:
UIImage *bottomImage = self.imageView.image;
UIImage *image = self.urlFoto.image;
CGSize newSize = CGSizeMake(640, 640);
UIGraphicsBeginImageContext( newSize );
[bottomImage drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:1.0];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
After this I add a method to resize image with pinch gesture:
- (IBAction)scaleImage:(UIPinchGestureRecognizer *)recognizer {
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
}
But when i save the Photo in photo library, i can't get the current size of my overlay and I see the same size 640,640 on overlay(image), i think the missed code is here:
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height) blendMode:kCGBlendModeNormal alpha:1.0];
On the CGRectMake(0,0,newSize.width,newSize.height) any know the correct method to get the current size of the UIImageView after pinched?

Answer 1

When drawing, you must keep the scale transform in mind. So you have to draw your overlay image with the respect to the final scale of the UIImageView adjusted by gesture.
You can get final scale of view like this:
CGFloat scale = view.transform.a;
The letter a is important here. It is value of the width transformation. So you can use it to get common scale assuming you are scaling the image proportionally (same scale for width and height)
Little more details regarding the scale:
CGAffineTransform is structure defined like
struct CGAffineTransform {
CGFloat a, b, c, d;
CGFloat tx, ty;
};
and
CGAffineTransformMakeScale(CGFloat sx, CGFloat sy)
does following according to the documentation
Return a transform which scales by `(sx, sy)':
t' = [ sx 0 0 sy 0 0 ]
For better understanding, see this example code:
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];
view.backgroundColor = [UIColor redColor];
[self.view addSubview:view];
view.transform = CGAffineTransformScale(view.transform, 0.5, 0.5);
NSLog(#"Transform 1: %f", view.transform.a);
view.transform = CGAffineTransformScale(view.transform, 0.5, 0.5);
NSLog(#"Transform 2: %f", view.transform.a);
which prints following to the console:
Transform 1: 0.500000
Transform 2: 0.250000
1st transform makes 0.5 scale to the default scale 1.0
2nd transform makes 0.5 scale to the already scaled 0.5 -> multiplies current 0.5 with new 0.5 scale
etc.

Answer 2

Step 1 : Declare in .h file
CGFloat lastScale;
Step 2 : in .m File replace your gesture method
- (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];
// Calculate the New Scale of UIImageView
CGFloat newScale = 1 - (lastScale - [gestureRecognizer scale]);
// Store Your Imageview's transform
CGAffineTransform transorm = simageView.transform;
// Convert your Imageview to Identity (original Size)
[imageView setTransform:CGAffineTransformIdentity];
// Save Rect Of UIImageView
CGRect actualRect = self.view.frame;
// Apply Transform to Imageview to make it scaled
[imageView setTransform:transorm];
// Now calculate new frame size of your ImageView
NSLog(#"width %f height %f",(imageView.frame.size.width*newScale), (imageView.frame.size.height*newScale));
}
}