Rotate image on center using one finger touch - iphone

Question

I want to rotate the below image on a center point using one finger touch...
And i want to display the value of the image with the label when I rotate the image using touch.
I have done the image rotation but the problem is that how to set the value of the image according to rotation.
The angle of the rotation is increase so i can not set the value.
Can any one help me?
The code is below
float fromAngle = atan2(firstLoc.y-imageView.center.y,
firstLoc.x-imageView.center.x);
NSLog(#"From angle:%f",fromAngle);
float toAngle = atan2( currentLoc.y-imageView.center.y,
currentLoc.x-imageView.center.x);
NSLog(#"to Angle:%f",toAngle);
// So the angle to rotate to is relative to our current angle and the
// angle through which our finger moved (to-from)
float newAngle =angle+(toAngle-fromAngle);
NSLog(#"new angle:%.2f",newAngle);
CGAffineTransform cgaRotate = CGAffineTransformMakeRotation(newAngle);
imageView.transform=cgaRotate;
angle = newAngle;
Can any one help me ?

Answer 1

Wasn't totally sure what you were after; but try out this code.
If you create a new View-based Application project called 'Rotation' and replace the code in RotationViewController.h and .m for the following you'll get a green block that you can rotate using your calculations. You can replace the green block UIView with your UIImageView, or anything else you want to spin.
RotationViewController.h
#import <UIKit/UIKit.h>
#interface RotationViewController : UIViewController
{
UIView* m_block;
UILabel* m_label;
CGPoint m_locationBegan;
float m_currentAngle;
}
- (float) updateRotation:(CGPoint)_location;
#end
RotationViewController.m
#import "RotationViewController.h"
double wrapd(double _val, double _min, double _max)
{
if(_val < _min) return _max - (_min - _val);
if(_val > _max) return _min - (_max - _val);
return _val;
}
#implementation RotationViewController
- (void)viewDidLoad
{
[super viewDidLoad];
CGRect blockFrame = CGRectMake(0, 0, 200, 200);
m_block = [[UIView alloc] initWithFrame:blockFrame];
m_block.backgroundColor = [UIColor greenColor];
m_block.center = self.view.center;
[self.view addSubview:m_block];
[m_block release];
CGRect labelFrame = CGRectMake(0, 0, 320, 30);
m_label = [[UILabel alloc] initWithFrame:labelFrame];
m_label.text = #"Loaded";
[self.view addSubview:m_label];
}
- (void) touchesBegan:(NSSet *)_touches withEvent:(UIEvent *)_event
{
UITouch* touch = [_touches anyObject];
CGPoint location = [touch locationInView:self.view];
m_locationBegan = location;
}
- (void) touchesMoved:(NSSet *)_touches withEvent:(UIEvent *)_event
{
UITouch* touch = [_touches anyObject];
CGPoint location = [touch locationInView:self.view];
[self updateRotation:location];
}
- (void) touchesEnded:(NSSet *)_touches withEvent:(UIEvent *)_event
{
UITouch* touch = [_touches anyObject];
CGPoint location = [touch locationInView:self.view];
m_currentAngle = [self updateRotation:location];
}
- (float) updateRotation:(CGPoint)_location
{
float fromAngle = atan2(m_locationBegan.y-m_block.center.y, m_locationBegan.x-m_block.center.x);
float toAngle = atan2(_location.y-m_block.center.y, _location.x-m_block.center.x);
float newAngle = wrapd(m_currentAngle + (toAngle - fromAngle), 0, 2*3.14);
CGAffineTransform cgaRotate = CGAffineTransformMakeRotation(newAngle);
m_block.transform = cgaRotate;
int oneInFifty = (newAngle*50)/(2*3.14);
m_label.text = [NSString stringWithFormat:#"Angle: %f 1in50: %i", newAngle, oneInFifty];
return newAngle;
}
#end