Previously if we found vectors of any sort on a page, we would bump
the DPI up to 400. We did nothing
about pages with text. As a result,
pages with a low image resolution
and printable text would have the text downgraded to image
resolution when --force-ocr was used.
We don't try to determine if the text is visible or invisible OCR text, since
that is a slower test. --redo-ocr would improve such cases anyway.