Вы можете сделать это как
static inline double radians (double degrees) {return degrees * M_PI/180;}
UIImage* rotate(UIImage* src, UIImageOrientation orientation)
{
UIGraphicsBeginImageContext(src.size);
CGContextRef context = UIGraphicsGetCurrentContext();
if (orientation == UIImageOrientationRight) {
CGContextRotateCTM (context, radians(90));
} else if (orientation == UIImageOrientationLeft) {
CGContextRotateCTM (context, radians(-90));
} else if (orientation == UIImageOrientationDown) {
// NOTHING
} else if (orientation == UIImageOrientationUp) {
CGContextRotateCTM (context, radians(90));
}
[src drawAtPoint:CGPointMake(0, 0)];
return UIGraphicsGetImageFromCurrentImageContext();
}
Взято из здесь