I'm trying to make a simple header image for my website, but I'm having a slight problem. Basically, I just am putting a curve on one corner of the image with a black background behind it. To do this, I made a rounded rectangle shape over a black background, then pasted the image into the shape. Doing so, however, produces a fuzzy white line along the curve. It's hard to explain, but take a look at the attached image to see what I mean. I'd really appreciate any help. Thank you!