On 20/11/2020 07:34, Arlen Holder wrote:
[...]
I didn't know that the scanner software creates the JPEG first.
And only after creating the JPEG does it save to PDF.
As far as I understand it, PDF is just a wrapper around many formats,
including JPEG, PNG, etc. The only things which are "native" are fonts,
text, and vector graphics. But that's just the bits I use; PDF can do
lots of other things.
I figured the scanner software made the image in its own internal format.
I think the scanner's internal firmware does indeed use its own format
(HP hardware has its own internal language, so do other manufacturers).
But what format the data is in during its transfer from scanner to
software I have no idea.
Which, for Irfanview, could be JPEG for all I know (as I don't know).
Desktop software probably lets you pick (somewhere) what format to save
the file as. I use XSane which does this:
http://www.silmaril.ie/downloads/xsane-settings.png
Does this imply that scanning & then saving as a JPEG results in better quality than scanning and then saving the document as a PDF?
That would really depend on the software settings. I don't know what compression PDF applies to embedded JPEGs. My software delivers the raw, uncompressed data for saving, so the files are huge, but every dot is
there. Typically I then need to edit the file to correct alignment,
colour, and crop, so I then save uncompressed if it's for print
publication (full-resolution, best quality, but still huge), or 50% compression, which is much smaller, lower resolution, but still
perfectly acceptable for other applications.
The real advantages of a PDF are:
• you avoid the small PDF wrapper overhead
• many computer users don't know what to do with a JPEG (weird when
you consider that's what their camera produces)
• you can put multiple images into a single PDF
• you can create a PDF via WP or DTP software so you can have text
and images combined
If you have a workflow that works, I'd stay with it.
Peter
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