When I create fills with linear and rainbow effects in Xara they look just the way I want them to look. However, when I export the drawing in png format and upload it to my server making it the background image of my website, there seems to be lines or creases. How can I smoothen the image so that the color flows nicely like it does in xara extreme pro? In my website, you'll see lines that do not appear in the original drawing in Xara extreme pro.