I'd like to hide some parts of the pictures, that I import to keynote presentation (I use version 6.2 (1861)). To do this I overlay white rectangles without shades on top of these parts of the images and use white color as a background color of the slide.
However, when I convert a slide with an overlaid rectangle (although the background is white and the rectangle is filled with white) I get an artifact: thin edge line of the rectangle in black on my pdf. How can I get rid of it?