How to draw a line with exact x and y positions? - iphone

Question

I need to work on a drawing application by using default delegate methods touches begin and touches moved.
But when I draw a line at any point of the screen, their x and y positions are changed automatically.
Actual problem in my application is: I draw a line at one position but that line is displayed in another place. What do I have to do to solve this problem?
My code is:
drawImage = [[UIImageView alloc] initWithImage:nil];
///drawImage.frame=CGRectMake(0,0, 320, 380);
drawImage.frame = self.view.frame;
[self.view addSubview:drawImage];
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"touches moved method");
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
currentPoint.y -= 20;
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
///[drawImage.image drawInRect:CGRectMake(0, 0, 320, 380)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), components[0],components[1],components[2],alpha);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
///mouseMoved++;
mouseMoved++;
if (mouseMoved == 10)
{
NSLog(#"if mouse moved is equal to 10");
mouseMoved = 0;
}
NSLog(#"touches moved method ended");
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
NSLog(#"touches Ended method starting");
UITouch *touch = [touches anyObject];
if ([touch tapCount] == 2)
{
NSLog(#"touches tap count==2");
///drawImage.image = nil;
return;
}
if(!mouseSwiped)
{
NSLog(#"not equla mouse swiped");
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
///[drawImage.image drawInRect:CGRectMake(0, 0, 320, 380)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
if (tagindex==1)
{
NSLog(#"1111");
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
}
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
}
Thanks in Advance

Answer 1

try to substitute
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
with
UIGraphicsBeginImageContext(drawImage.frame.size);
[self.firma.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)];
and if u don't have the status bar, remove: currentPoint.y -= 20;
hope this is the problem.