It appears that extractText() does not find all text. At a glance it
may be that Tesseract's PDF renderer generates a font and uses glyphs
that map to different Unicode code points that PyPDF expects, so it
discards the content and finds nothing. As a proxy in lieu of better
PDF parsing, assume that a "GlyphLessFont" means there is a text there.
I had previously found it does not work to check for the presence of a
font on page. Some PDF generators create a font resource entry even if
the font is never called for.
Someone reported a bug where the .png input to unpaper ended up being
type 'P' (palette) for some reason, which was not supported in unpaper.
Not sure how it happened, but seemed easier to fix by explicitly
supporting. Here we use png256 if it would capture all colors in the
input file. It's up to tesseract/reportlab to make use of the palette
PNG when rendering.
James R. Barlow