Drawing with finger on UIImageView that does not cover entire screen - ios

Question

I have managed to get drawing on top of a recently captured UIImage working, but it only works when the UIImageView covers the entire screen. It begins to lose accuracy the moment I start drawing away from the horizontal center. Any idea how I can get it to only work on the ImageView itself and have it remain accurate?
- (void)viewDidLoad
{
[super viewDidLoad];
float height = (self.view.frame.size.width * self.chosenImage.size.height)/self.chosenImage.size.width;
self.imageView.frame = CGRectMake(0, self.navigationController.navigationBar.frame.size.height, self.view.frame.size.width, height);
self.imageView.center = self.imageView.superview.center;
self.imageView.image = self.chosenImage;
}
- (UIImage *)drawLineFromPoint:(CGPoint)from_Point toPoint:(CGPoint)to_Point image:(UIImage *)image
{
CGSize sizeOf_Screen = self.imageView.frame.size;
UIGraphicsBeginImageContext(sizeOf_Screen);
CGContextRef current_Context = UIGraphicsGetCurrentContext();
[image drawInRect:CGRectMake(0, 0, sizeOf_Screen.width, sizeOf_Screen.height)];
CGContextSetLineCap(current_Context, kCGLineCapRound);
CGContextSetLineWidth(current_Context, 1.0);
CGContextSetRGBStrokeColor(current_Context, 1, 0, 0, 1);
CGContextBeginPath(current_Context);
CGContextMoveToPoint(current_Context, from_Point.x, from_Point.y);
CGContextAddLineToPoint(current_Context, to_Point.x, to_Point.y);
CGContextStrokePath(current_Context);
UIImage *rect = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return rect;
}
- (void)touchesBegan:(NSSet *)_touches withEvent:(UIEvent *)_event
{
// retrieve the touch point
UITouch *_touch = [_touches anyObject];
CGPoint current_Point = [_touch locationInView:self.imageView];
// Its record the touch points to use as input to our line smoothing algorithm
self.drawnPoints = [NSMutableArray arrayWithObject:[NSValue valueWithCGPoint:current_Point]];
self.previousPoint = current_Point;
// we need to save the unmodified image to replace the jagged polylines with the smooth polylines
self.cleanImage = self.imageView.image;
}
- (void)touchesMoved:(NSSet *)_touches withEvent:(UIEvent *)_event
{
UITouch *_touch = [_touches anyObject];
CGPoint current_Point = [_touch locationInView:self.imageView];
[self.drawnPoints addObject:[NSValue valueWithCGPoint:current_Point]];
self.imageView.image = [self drawLineFromPoint:self.previousPoint toPoint:current_Point image:self.imageView.image];
self.previousPoint = current_Point;
}
EDIT: With these settings I have accuracy in the UIImageView, but the image blurs inwards as I am drawing.
When I edit [image drawInRect:CGRectMake(0, 0, sizeOf_Screen.width, sizeOf_Screen.height)]; to be [image drawInRect:CGRectMake(0, self.imageView.frame.origin.y, sizeOf_Screen.width, sizeOf_Screen.height)]; and try to draw, the image flies off out of the view when I try to draw.
I've tried tweaking the sizeOf_screen value and CGRectMake of image in the drawLineFromPoint method. I've also attempted to set the locationInView in both instances to self.imageView, but to no avail. It's very strange. Any ideas or code samples that might accomplish what I'm looking for? I can't seem to find anything.