Q:

OpenGLES 2.0 Rotate by touchesMoved

I want to use the touchesMoved method to rotate an image on the screen. 
So if i move my finger from the right to the left side, i want my
image to rotate from left to right. 
Is this somehow possible? 

A:

Found a solution! 
- (void)handleDragFrom:(CGPoint)start to:(CGPoint)end
{
    [super handleDragFrom:start to:end];

    float rotationCenterX = self.player.position.x - (self.player.contentSize.width / 2);
    float rotationCenterY = self.player.position.y - (self.player.contentSize.height / 2);

    float dXStart = start.x - rotationCenterX;
    float dYStart = start.y - rotationCenterY;
    float radianStart = atan2(dYStart, dXStart);

    float dXEnd = end.x - rotationCenterX;
    float dYEnd = end.y - rotationCenterY;
    float radianEnd = atan2(dYEnd, dXEnd);

    float radian = GLKMathRadiansToDegrees(radianEnd - radianStart);

    self.player.rotation -= radian;
}

"start" and "end" are the two points given from touches moved:
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event allTouches] anyObject];

    CGPoint end = [touch locationInView:self.view];
    CGPoint start = [touch previousLocationInView:self.view];

    [self.scene handleDragFrom:start to:end];
}

