As far as browser extensions, if you want image perfect capture stick with GoFullPage. If you're more leaning to a much smaller size' getting the text, getting clickable links and in a pdf format, try:
@brupp are you referring to a local html file or are you talking about taking a screenshot from a given url, but using DOpus?
For the latter, you can use the https://htmlcsstoimage.com API from DO itself. It seems promising, at least in some tests I did. (And is free for up to 50 images per month)
I am refering to taking a HTML directory representing a screenshot and converting it to a single png file.
I have this problem because I am exporting notes from Evernote and they provide a single page HTML output option - so thjat is what I want to copnvert to a PNF.
In any case I will take a lok at the utility you suggested.