PCJS has some kind of post processing done to the output image. I needed some pixel perfect screenshots of Win 3.1 the other day, and the ones I took from PCJS were blurred (maybe upscaled?) compared to the ones I took of VMWare.
That's just the HTML canvas element and poor scaling. You can use your browser's inspector to clean up the `width`/`height` style attributes and add `image-rendering: pixelated`...