How To Rotate an UIImageView based on a point in Touches Moved Method? - iphone

Question

Dear All,
I want to rotate a UIImageView relative to a point in touchesMoved method.
I tried 2 -3 methods but I am not getting the exact result what I expected to be.
First method I used
CGAffineTransform transforms = CGAffineTransformMakeRotation(M_PI/2);
imgView.transform = transforms;
This is written in touchesMoved. So I expect a rotation for the image view in each touchesMoved.
But the rotation is occuring only once .
Second method I used was
CGAffineTransform transforms = CGAffineTransformRotate(imgView.transform, M_PI/2);
imgView.transform = transforms;
Now the result what I get is the image in Image view is continusely rotating in each move. But imageview is not rotating. What i need is to rotate the imageview not the image.
Any help will be greatly appreciated.
Thanks & Best Regards,
Rupesh R Menon

Answer 1

If I understood correctly you want to achieve single finger rotation on the image. If it is so you can use following functions from one of my live working project. You can use this for single image as well as multiple images. You need to modify at some extend for multiple images. Best way is extend UIImageView class and create your own class.
From touches moved call this function
[self transformImagewithTouches:touch];
Declare 1 property and synthesize as follows. (Also please declare other variables if required in below code.
#property (nonatomic) CGFloat fltRotatedAngle;
-(void)transformImagewithTouches:(UITouch *)touchLocation
{
//NSLog(#"Before %f",self.fltRotatedAngle);
CGPoint touchLocationpoint = [touchLocation locationInView:[self superview]];
CGPoint PrevioustouchLocationpoint = [touchLocation previousLocationInView:[self superview]];
CGPoint origin;
origin.x=self.center.x;
origin.y=self.center.y;
CGPoint previousDifference = [self vectorFromPoint:origin toPoint:PrevioustouchLocationpoint];
CGAffineTransform newTransform =CGAffineTransformScale(self.transform, 1, 1);
CGFloat previousRotation = atan2(previousDifference.y, previousDifference.x);
CGPoint currentDifference = [self vectorFromPoint:origin toPoint:touchLocationpoint];
CGFloat currentRotation = atan2(currentDifference.y, currentDifference.x);
CGFloat newAngle = currentRotation- previousRotation;
//Calculate Angle to Store
fltTmpAngle = fltTmpAngle+newAngle;
self.fltRotatedAngle = (fltTmpAngle*180)/M_PI;
newTransform = CGAffineTransformRotate(newTransform, newAngle);
[self animateImageView:self toPosition:newTransform];
}
-(void)animateImageView:(UIImageView *)theView toPosition:(CGAffineTransform) newTransform
{
[UIView setAnimationsEnabled:YES];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:0.0750];
self.transform = newTransform;
[UIView commitAnimations];
}
-(CGPoint)vectorFromPoint:(CGPoint)firstPoint toPoint:(CGPoint)secondPoint
{
CGFloat x = secondPoint.x - firstPoint.x;
CGFloat y = secondPoint.y - firstPoint.y;
CGPoint result = CGPointMake(x, y);
return result;
}
Hope it helps. If you stuck up please let me know I ll definitely help you.

Answer 2

Thanks for the interest shown by you in helping me.
When I used the following code I was able to rotate the image view in my desired angle.
imgView.layer.transform = CATransform3DMakeRotation(pCalculator.tangentToCornerAngle, 0, 0, 1);
where imgView is an UIImageView.
pCalculator.tangentToCornerAngle is the desired angle in which rotation has to be made.
Function is CATransform3DMakeRotation(CGFloat angle, CGFloat x, <CGFloat y, CGFloat z);
Thankyou All,
Rupesh R Menon

Answer 3

It's because you have rotated it by M_PI/2 and when you rotate it again it rotates it from the initial position. Use this one
CGAffineTransform transforms = CGAffineTransformConcat(imgView.transform,CGAffineTransformMakeRotation(M_PI/2));
imgView.transform = transforms;