Importing images into Edge Animate: sharpness problems

I have some small PNG images, maybe 180px  x  350px each. They are very sharp when viewed either in Photoshop, or as stand-alone images on a web page. They are PNG-24, color.

When I import them into Edge Animate, even if I do not modify them at all, they are noticeably less sharp when embedded in an animation (html) file. The only things I am planning to do with these images is to insert some opacity transitions, but the sharpness issue must be addressed first.

I am importing as PNG files.

Is there a better/preferred way to handle thse small bitmap as elements on an Edge animation?

TIA!