How to implement drawing tool in iOS? - ios

Question

I'm trying to implement a freehand drawing tool by which user can draw several shapes dynamically like rectangle,eclipse,circle etc on a PDF using touch begins and touch move methods.
So anyone there who have done this kind of tool or have knowledge how to accomplish this,please help me out.
Thank you in advance.

Answer 1

This is a very broad question to be answered on StackOverflow. Still I am trying to give you a start here.
1) Declare two global variables BOOL mouseSwiped, CGPoint lastPoint in your UIViewController.
2)
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.view];
}
3)
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(yourSubview.frame.size);
[yourSubview drawInRect:CGRectMake(0, 0, yourSubview.frame.size.width, yourSubview.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 3.0 );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
yourSubview = UIGraphicsGetImageFromCurrentImageContext();
[yourSubview setAlpha:1.0];
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
4)
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
UIGraphicsBeginImageContext(yourSubview.frame.size);
[yourSubview drawInRect:CGRectMake(0, 0, yourSubview.frame.size.width, yourSubview) blendMode:kCGBlendModeNormal alpha:1.0];
yourSubview = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
Hope this helps