Re: [gentoo-user] compressing pdf file

thelma@×××××××××××.com <thelma@×××××××××××.com> [17-02-23 02:57]:
> On 02/22/2017 03:12 PM, karl@××××××××.se wrote:
> > Thelma:
> >> I have scaned pdf file (88-page) 23MB in size (downloaded this way).
> >> Trying to reduce the size of the file I [...]
> >
> > Why don't you extract the images with pdfimages from the pdf and
> > compress them with xv or convert (imagemagic) and maybe gimp can
> > comress them also. Don't know how to get them back into a pdf though.
> >
> > Regards,
> > /Karl Hammar
> >
> > -----------------------------------------------------------------------
> > Aspö Data
> > Lilla Aspö 148
> > S-742 94 Östhammar
> > Sweden
> > [phone]
>
> I'm puzzled as to what program they used to compress the PDF file with such a good quality output (PDF format as well).
>
> This is the link I use to compress the file:
> https://online2pdf.com/pdf-reduce-size
>
> I've tried:
> gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dDownsampleColorImages=true -dColorImageResolution=150 -dNOPAUSE  -dBATCH -sOutputFile=5.pdf COVERAGE_July-1-2016.pdf
>
> gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=5.pdf COVERAGE_July-1-2016.pdf
>
> convert -density 200x200 -quality 60 -compress jpeg COVERAGE_July-1-2016.pdf 5.pdf
>
> gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=5.pdf COVERAGE_July-1-2016.pdf
>
> The last one above gave me decent size I think about 5MB but the quality wasn't very good.
> All others, size was hardly reduced or quality was terrible.
>
> Gimp will open only one page at at time, so it is not suitable for this conversion.
>
> --
> Thelma
>
>

Hi Thelma,

may be it would gave you a hint, what happens to the PDF while
compressing, so it is easier to duplicate the result.

I think, the pdf which was the direct result of the scanning
process is a series of images in a kind of pdf container.

May be you will find a site on the internet (I dont know
of any program on Gentoo, which does this) which is 
able to analyse the structure of a pdf.

May the result of that analyses will give you a hint,
what magic the compression process has done.

By the way: What did you scann? Pure Text? Images
only? A mixture of both? Line drawings?

Did you find traces of an ocr process like mispelled
word and/or missing character?

HTH!
Cheers
Meino