A specific drawing field in a viewcontroller - Objective C - ios

Question

I am making an application where the user sign an form with their signature (analog, with stylus) and I am having this code:
In .h:
CGPoint lastPoint;
CGPoint movebackTo;
CGPoint currentPoint;
CGPoint location;
NSDate *lastClick;
BOOL mouseSwiped;
UIImageView *drawImage;
And in .m
- (void)viewDidLoad {
NSUserDefaults *preferences = [NSUserDefaults standardUserDefaults];
drawImage.image = [preferences objectForKey:#"drawImageKey"];
drawImage = [[UIImageView alloc] initWithImage:nil];
drawImage.frame = CGRectMake(0, 0, 768, 1024);
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches] anyObject];
if ([touch tapCount] == 3) {
drawImage.image = nil;
}
location = [touch locationInView:self.view];
lastClick = [NSDate date];
lastPoint = [touch locationInView:self.view];
lastPoint.y -= 0;
[super touchesBegan: touches withEvent: event];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(CGSizeMake(768, 1024));
[drawImage.image drawInRect:CGRectMake(0, 0, 768, 1024)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.8, 0.8, 0.8, 1);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
[drawImage setFrame:CGRectMake(0, 0, 768, 1024)];
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
[self.view addSubview:drawImage];
}
The problem is, this works fine if I want to use the WHOLE screen for drawing. But I want to use a specific part of the view as "drawing box. I already tried things like changing the line: [drawImage.image drawInRect:CGRectMake(0, 0, 768, 1024)]; to CGRectMake(58, 623, 240, 143)]; Which is the size and position the box has to be, but this is not working for me.
What happens when i change those kind of things: i can draw in the leftcorner of the view, but the actual lines display in the right box! But the drawing, plus the displaying of the code has to be in the box which is located at: X-58 y-623 and is W240 and H143.
I've searched the whole web for this specific thing but I could not find a good answer for this.
I hope you guys can help me out! It would be appreciated very much!