Rendering touchesMoved and Fingerpaint slow - iOS7 - rendering

Question

I have a app that allows fingerprinting. For this I use touchesBegan, touchesMoved, touchesEnded. On iOS6 it works smooth, when moving the finger, the line is painted. But on iOS7, only the first point from touchesBegan is painted and on touchesEnded, the line is painted.
Does anyone has a similar issue and/or solution.
(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:drawImage];
// currentPoint.y -= 20; // only for 'kCGLineCapRound'
UIGraphicsBeginImageContext(drawImage.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 30.0); // for size
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 1.0, 1.0); //values for R, G, B, and Alpha
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
mouseMoved++;
if (mouseMoved == 10) {
mouseMoved = 0;
}
}
EDIT and solution!
Don't try to draw or call draw routines inside the touch delegates. The newer devices might support faster and higher resolution touch detection, and thus your app might be getting touch messages way to fast to draw in time, thus choking your UI run loop. Trying to update faster than 60 fps can do that.
Instead save your touch data points somewhere, and then draw later, for instance inside a polling animation loop callback (using CADisplayLink or a repeating timer), outside the touch handler, thus not choking the UI.
Comment from Lawrence Ingraham in Apple Developer Forum
Based on this, I have made the following changes:
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
currentPoint = [touch locationInView:self.view];
[self performSelector:#selector(drawFinger) withObject:nil afterDelay:0.0];
}
- (void)drawFinger
{
UIGraphicsBeginImageContext(imgDibujo.frame.size);
[imgDibujo.image drawInRect:CGRectMake(0, 0, imgDibujo.frame.size.width, imgDibujo.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), delegate.lineAncho); // for size
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), delegate.colorR, delegate.colorG, delegate.colorB, delegate.colorS); //values for R, G, B, and Alpha
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
imgDibujo.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
It works now perfect on all iPad devices. Hope that this is helpfully for you.