Re: Reducing the size of a pdf file

On Aug 28, 1:40 pm, Hans-Werner Hilse <hi...@xxxxxx> wrote:
Hi,

On Tue, 28 Aug 2007 12:15:52 -0000 phh...@xxxxxxxxx wrote:

I have a scanned book with 500 pages in a pdf file. The size of the
file is about 90 MB. Is there some way of reducing the size of the pdf
file? I am using Linux.

That certainly depends.
- your Images might not have optimal depth or they might not (yet) use
the best (as for size) compression scheme,
- you might accept lossy compression, in which case it's a deal between
quality and size,
- it might be OK for you to reduce the images' resolution.

On Linux, I'd extract the images using pdfimages (comes with the
poppler library, older versions are in the Xpdf toolchain). Then I'd
compress them to tiff images, chosing the best possible compression
scheme (e.g. G4 for b/w images), using the libtiff tools, and do other
steps, if needed. I'd then recreate the PDF using tiff2pdf. This is the
way for lossless compression, of course.

You might also want to test JPEG2000 on your images -- though I
currently don't have a good suggestion regarding the tool to assemble
the images back to a PDF.

There's also DjVu, which is very well suited for this task, but you'd
be leaving PDF waters at that point.

As a side note: 90MB/500 scanned pages sounds pretty reasonable, so you
might already have the best compromise.

Thanks, Hans-Werner and Ken, for your very detailed and helpful
replies. I have meanwhile converted to ppm the pdf file with
pdfimages. However, when I try to convert to tif, I get the following
error:

$ ppm2tiff -c g4 pag-160.ppm pag-160.tif
pag-160.tif: Error writing TIFF header.
$

Any ideas?

Paul

.

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