pen&ink filter rendering final image as BMP

Hi there. Relatively new to FF. I downloaded the pen and ink crosshatch filter by northernshadow. When I final render my image and save it as a .png and then open it in Photoshop it displays as a BMP; in other words zooming in I can see the individual pixel blocks one would see with a bitmap image. Is there a way to final render with anti alias. I have custom inking brushes that I use in PSD and my intent is to "work over" this image, enhancing and simplifying things. Those inking brush strokes go down as anti aliased strokes and consequently don't match the FF rendered image.

Any help or advice is greatly appreciated. Thanks.