He entendido su problema. Por favor, vea el código de abajo. Utilizará lleno para usted.
-(void)intializeDrawImage
{
drawImage = [[UIImageView alloc]initWithFrame:CGRectMake(0, 100, 320, 320)];
[drawImage setBackgroundColor:[UIColor purpleColor]];
[drawImage setUserInteractionEnabled:YES];
[self.view addSubview:drawImage];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(@"touchesBegan");
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:drawImage];
startPoint = p;
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(@"touchesMoved");
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:drawImage];
[self drawLineFrom:startPoint endPoint:p];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesMoved:touches withEvent:event];
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesEnded:touches withEvent:event];
}
-(void)drawLineFrom:(CGPoint)from endPoint:(CGPoint)to
{
drawImage.image = [UIImage imageNamed:@""];
UIGraphicsBeginImageContext(drawImage.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)];
[[UIColor greenColor] set];
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0f);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), from.x, from.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), to.x , to.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
Usted debe echar un vistazo a la aplicación de demostración [GLPaint] (http://developer.apple.com/library/ios/#samplecode/GLPaint/Introduction/Intro.html), de Apple. Le enseñará los conceptos básicos de la pintura con un solo dedo con OpenGL ES. – Macmade
Pruebe UIBezierpath. Este tutorial puede ser útil para usted. http://soulwithmobiletechnology.blogspot.in/2011/05/uibezierpath-tutorial-for-iphone-sdk-40.html –
Otro buen ejemplo se puede encontrar aquí: este controlador proporciona la entrada de una firma y devuelve una imagen. Además, se proporciona un ejemplo de trabajo: https://github.com/bunchjesse/JBSignatureController –