[MikeWV]

How does one create an ePub cover image that preserves text clarity when scaled to fit various screens, and for bookshelf and thumbnail images? I've searched and searched for an answer to this seemingly simple question and have yet to find an answer.

I'm, using a PNG image in an SVG wrapper. The image file was created from an Excel chart using XL Toolbox, which creates a publication quality PNG. Sometimes the text looks good and sometimes it doesn't. It looks great at full scale in IrfanView and almost as good in MS photo Viewer, but not so good in some of the reading software.

It looks real good as a basic SVG image, when it works. But as noted in a recent thread, a pure SVG cannot be used dependably as a cover. I've tried it and found that even when it works as a cover, it doesn't work as a bookshelf cover and presumably not for thumbnails, either.

I've found plenty of advice on what fonts to use and not use but nothing addressing the preservation of the clarity of the text. I know this is a problem with raster-type files but this problem has obviously been overcome somehow, I just can find anything explaining how it's been overcome.

Your input will be greatly appreciated.