Pixels with round shape?

Is there a way to have the pixels in a bitmap generated with the image operator in a round shape? Ideally the round pixels shall have smooth edges.

Background: I want to convert existing legacy graphic prints on a Printronix P8000 matrix line printer to PDF. For this I have written a C-program converting the P8000 graphics to PostScript and subsequently to PDF. All this works very nicely now. The graphics are well usable. But the clean pixel graphics in PDF with exactly squared pixels does not look as pleasant as the old graphics on the hardware printer with round pixels looking like smeared circles.