drawRect in Custom UIView off by height of navigation bar

I'm drawing a custom UIView that is sitting inside a xib whose ViewController is pushed onto a NavigationController.

Essentially the problem is that in the call to drawRect:(CGRect)rect, rect has origin at (0,0) when it should have origin at (0,nav_bar_height). Therefore, the following code, which draws an image

- (void)drawRect:(CGRect)rect {

    CGContextRef context = UIGraphicsGetCurrentContext();
    UIGraphicsPushContext(context);

    // set up the image
    UIImage * img = [UIImage imageWithData:someData];

    // flip the image to the correct orientation
    CGContextTranslateCTM(context, 0, rect.size.height + rect.origin.y );
    CGContextScaleCTM(context, 1, -1);

    // draw the image
    CGContextDrawImage(context, rect, [img CGImage]);

    UIGraphicsPopContext();

}

This will cut off the top 30 pixels or so of the imag开发者_高级运维e and leave empty the bottom 30.

How can I account for the navigation bar height?

Without knowing more about your view-structure, I risk being unhelpful, but let me know if the following helps at all: instead of using the rect parameter, which can be sort of unpredictable, try using the bounds of your custom view. In reality, I can't imagine why you'd be having this problem, unless your view is being overlapped with the navigation bar; I'd suggest checking to be sure this isn't so, in any case. Best of luck!

Update

Looks like that didn't help. Just offset your y parameter by self.navigationController.navigationBar.bounds.size.height. So your code should look like:

//...
CGFloat dy = self.navigationController.navigationBar.bounds.size.height;
CGRect r = CGRectMake(rect.origin.x,rect.origin.y + dy, rect.size.width, rect.size.height - dy);
//...
CGContextDrawImage(context,r,img.CGImage);
//...

I hope that was more helpful.