31 Dec
2011
31 Dec
'11
9:56 a.m.
On 31/12/11 6:35 AM, arcarlini at iee.org wrote:
David Griffith [dgriffi at cs.csubak.edu] wrote:
Good advice. Most people know by now that PDF can encode this directly too.
Since several people here do this kind of thing,
I figured
I'd ask here.
I'm trying my hand at scanning stuff to PDF. The only thing
I seem to
find for doing this in Linux is Simple Simple Scan. I'm scanning in
photo mode because text mode is unacceptably grainy. My problem now
is converting the resulting jpg into a pdf. ImageMagick is the
obvious tool for this, but no matter what I do, the resulting pdf is
grainy. How can I
tell ImageMagick to not diddle with the quality?
The first thing to say id that if you are scanning text JPEG is not what
you want.
You probably want TIFF, specifically G4 encoded bi-level (i.e. B&W
rather than
grey scale). If there are photographs then you might want 8-bit
grey
scale
(although I've very rarely found it to make any difference, other than
to
file size).
I tend to scan @ 600dpi but anything above 400dpi seems visually
acceptable
(to me, I've no idea what anyone else thinks).
I agree. Diminishing returns, 400dpi is fully adequate for text. Any
more and the resulting files become cumbersome to store and especially
read (relatively slow e-readers are becoming commonplace!)
Pay attention to diagrams with fine lines. In tricky cases, changing the
black/white threshold might be necessary to prevent dropouts. For this
reason it can be good to scan in grey scale for later processing based
on evaluating some pages (possible resolution reduction, thresholding,
and compression).
--Toby
If you have colour photographs then you probably want JPEG, but only for
those
pages. For DEC manuals, I've mostly found that only the covers need
colour
scanning. There are some software manuals that have mostly black text
with the
occasional smattering of colour (or worse, blocks of text with a
background colour)
but I've never found a good way of handling those and preserving the
colour.
As for the actual scanning, I'm afraid I cannot help: my scanner
delivers the
resulting TIFF-wrapped-in-PDF via FTP :-)
Antonio