10 Sep
2001
10 Sep
'01
10:52 p.m.
Jim Battle wrote:
At 02:16 PM 9/10/01 -0700, you wrote:
excess. The KA655 TM
I don't know where 100dpi/8-bit came from -
its 600dpi/1-bit (apart from maybe one or two pages
which are 600dpi/8-bit). I don't know how
to persuade Acrobat to tell me what the
underlying resolution is, but I expect it's
possible!
that is on the DFWCUG site appears from the PDF to
be 100
DPI/8 bit (note
>that's 800 bits per inch net and the result is harder to I agree that 300 dpi @ 1bpp is superior for text and
line art
than 100 dpi
@ 8bpp, but I think your math is askew. You need to compare
the # of bits
per sq in, not inch. So 100 dpi @ 8bpp is 10KB/in^2, while
300 dpi @ 1bpp
is 11.25 KB/in^2. For text and line art, though, the 1bpp image will
compress a lot better.
I make 600dpi/1-bit to be a smidgen under 44KB/sq-in.
This is an A4 scan (of a photocopy of an original
which is less than A4 in all dimensions IIRC) so
thats 8.5x11.5in i.e. anything less than ~4MB/page
is compression kicking in! I think the pages
average something like 300KB/page.
I get PDF direct from the scanner but I don't think
it does G4 compression. If anyone has a tool which will
take in a PDF and spit out a G4-compressed PDF,
I'd be very interested. I think I've seen people
claim that 300dpi/1-bit scans run at about 60KB/page
so I assume that G4 compression would bring these
documents down to about 250KB/page (15-20% smaller).
Of course, "perfect" OCR would knock it down
a good deal more than that!
Antonio
And if, for some reason, you want to scan line art and text
in gray scale,
4bpp is plenty enough. Use 8bpp only for continuous-tone images.
Possibly true (although almost every page
that I use 8-bit for does have a photo
of some gubbin or other). But the scanner
spits out 1-bit or 8-bit and there are not
that many knobs available for tweaking.
Antonio