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Re: PDF: multiple slides per page to one slide per page?

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In article <5dfd7c91-cd2c-4cda-94b1-9f64fc1fab02
@h12g2000pro.googlegroups.com>, dmathog@gmail.com says...

>  gs -r720 -sDEVICE=tiff32nc -sOutputFile=out.tif  -dFirstPage=4 -
> dLastPage=4 test.pdf
> 
> Which produced a 190MB tiff.  Cut and pasted the "platonic" part (in
> Windows XP Paint) and made a side by side comparison with the original
> and the flate versions, here:
> 
>   http://saf.bio.caltech.edu/pub/pickup/platonic_3_versions.PNG
> 
> Interesting.  The pixel pattern is the same in the from_tif and
> original versions, but the colors are very slightly different.

Yes, that was what I was attempting to say in my earlier post. To me 
there doesn't appear to be any corruption per se, but the colours do 
look different. This is possible in JPEG where the high and low 
frequency components (edges and colours) are separate.

I tried the latest code here, at 300 dpi on Windows, and the result is 
most similar to the 'Platonic_original.PNG' in your screenshot. Not 
quite the same, but then PNG is potentially a lossy format too, which is 
why I suggested TIFF.

I also redid this using the tiff24nc device so that we don't get RGB->
CMYK->RGB conversion. I also zoomed in to 2400% in Acrobat with image 
smoothing turned off, again the 'Platonic_original.PNG' is the best 
match to Acrobat.

In fact at 600 dpi, tiff24nc (for RGB output) the result is 
indistinguishable from Acrobat's output.

This means its not the decompression of the JPEG file, so on to 
pdfwrite. 

Here I do see the kind of colour changes you describe, and to my eye 
they look to be the sort of artefacts caused by reapplying JPEG 
compression to data which has previously been JPEG compressed. And 
indeed if I decode the file I see that all 3 images within it are 
compressed with DCT. (NB I was using a very simple command line here).

I then used this command line:

gswin32c -sDEVICE=pdfwrite -dCompressPages=false -
dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -
sOutputFile=out.pdf -dFirstPage=4 -dLastPage=4 platonic.pdf

Checking the (uncompressed) PDF file I see that all three images are now 
compressed using Flate. Opening the file in Acrobat I see that the 
colour shifting has disappeared, and the area in question looks OK. In 
fact, comparing the two in Acrobat at 2400% zoom and image smoothing 
turned off they are again indistinguishable.

So it seems to me that the problem is that your ourput is still being 
DCT compressed. Can I ask you to try the command line above and see if 
that improves matters for you ?

Obviously on Linux you'll want to use 'gs' instead of gswin32c.

			Ken

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Re: PDF: multiple slides per page to one slide per page? pipitas <pipitas@googlemail.com> - 2011-04-25 04:35 -0700
  Re: PDF: multiple slides per page to one slide per page? pipitas <pipitas@googlemail.com> - 2011-04-25 05:55 -0700
  Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-21 15:03 -0700
    Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-22 15:35 -0700
      Re: PDF: multiple slides per page to one slide per page? ken <ken@spamcop.net> - 2011-06-23 07:56 +0100
        Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-23 13:56 -0700
          Re: PDF: multiple slides per page to one slide per page? ken <ken@spamcop.net> - 2011-06-24 07:57 +0100
            Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-24 09:33 -0700
              Re: PDF: multiple slides per page to one slide per page? ken <ken@spamcop.net> - 2011-06-24 20:05 +0100
              Re: PDF: multiple slides per page to one slide per page? ken <ken@spamcop.net> - 2011-06-25 11:51 +0100
                Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-27 10:21 -0700
                Re: PDF: multiple slides per page to one slide per page? ken <ken@spamcop.net> - 2011-06-28 08:08 +0100
                Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-27 10:33 -0700
                Re: PDF: multiple slides per page to one slide per page? David Mathog <dmathog@gmail.com> - 2011-06-28 09:22 -0700
                Re: PDF: multiple slides per page to one slide per page? mathog <dmathog@gmail.com> - 2011-06-30 10:34 -0700
                Re: PDF: multiple slides per page to one slide per page? tlvp <tPlOvUpBErLeLsEs@hotmail.com> - 2011-06-30 23:25 -0400

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