deleting every other line in an image

[Josh Mellicker]

Here's one for the image processing gurus out there:

How difficult is it to take an image, and create a new image  
containing every OTHER line from it (e.g., just the odd lines) so the  
resulting picture is half the height?

Once you knew the width of the image, isn't it just a loop that  
copies tWidth pixels, then skips the next tWidth, and so on?

Thanks!