iOS - Rotate UIImageView or UIImage while moving its frame with NSTimer - ios

Question

I need to rotate my UIImageView, or the UIImage in the UIImageView, while moving its frame with NSTimer. This is the NSTimer movement :
timer = [NSTimer scheduledTimerWithTimeInterval:time target:self selector:#selector(animate) userInfo:nil repeats:YES];
This is the animate method (a part of it, the most important) :
CGRect viewLocation = [[[self layer] presentationLayer] frame];
self.frame = CGRectMake(viewLocation.origin.x, viewLocation.origin.y + 0.2, viewLocation.size.width, viewLocation.size.height);
And this is the method i'm trying to use to rotate the UIImage :
- (UIImage *)imageRotatedByDegrees:(CGFloat)degrees
{
// calculate the size of the rotated view's containing box for our drawing space
UIView *rotatedViewBox = [[UIView alloc] initWithFrame:CGRectMake(0,0,self.size.width, self.size.height)];
CGAffineTransform t = CGAffineTransformMakeRotation(DegreesToRadians(degrees));
rotatedViewBox.transform = t;
CGSize rotatedSize = rotatedViewBox.frame.size;
[rotatedViewBox release];
// Create the bitmap context
UIGraphicsBeginImageContext(rotatedSize);
CGContextRef bitmap = UIGraphicsGetCurrentContext();
// Move the origin to the middle of the image so we will rotate and scale around the center.
CGContextTranslateCTM(bitmap, rotatedSize.width/2, rotatedSize.height/2);
// Rotate the image context
CGContextRotateCTM(bitmap, DegreesToRadians(degrees));
// Now, draw the rotated/scaled image into the context
CGContextScaleCTM(bitmap, 1.0, -1.0);
CGContextDrawImage(bitmap, CGRectMake(-self.size.width / 2, -self.size.height / 2, self.size.width, self.size.height), [self CGImage]);
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
This code is inside a subclass of UIImageView, so self is referred to UIImageView.
I also try to rotate UIImageView with CGAffineTransform, but the UIImageView is being stretched and rotate in a strange manner.
This is the method :
- (void)rotateWithDegrees:(CGFloat)degrees {
CGAffineTransform transform = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(degrees));
self.transform = transform;
}
And this is the macro :
#define DEGREES_TO_RADIANS(angle) (angle / 180.0 * M_PI)
The important thing is that you can always use the timer to move the object, so that part is unchangeable.

Answer 1

I found the solution! First of all we exclude the solution that provides the resize of UIImage. So, we rotate the UIImageView, but when use CGAffineTransform the frame have NOT to be modified! So, to move the UIImageView with the timer we have to modify the center of the UIImageView. This is to delete :
CGRect viewLocation = [[[self layer] presentationLayer] frame];
self.frame = CGRectMake(viewLocation.origin.x, viewLocation.origin.y + 0.2, viewLocation.size.width, viewLocation.size.height);
And this is to add :
self.center = CGPointMake(self.frame.origin.x + (self.frame.size.width / 2), self.frame.origin.y + 0.2 + (self.frame.size.height / 2));
Then, we can use the rotateWithDegrees: method to rotate the UIImageView :
- (void)rotateWithDegrees:(CGFloat)degrees {
CGAffineTransform transform = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(degrees));
self.transform = transform;
_degrees+=0.5;
if (_degrees == 360) {
_degrees = 1;
}
}
So, we can add the line :
[self rotateWithDegrees:_degrees];
below :
self.center = CGPointMake(self.frame.origin.x + (self.frame.size.width / 2), self.frame.origin.y + 0.2 + (self.frame.size.height / 2));
The UIImageView moves due to the change of its center, and not due to the change of its frame and this allow to use CGAffineTransform for the rotation.