[gs-devel] Default resolution not properly calculated for rasterpdf files xefitra

[Leonardo]

PDF is a resolution independent data format.
There is no default resolution in it.

If a PDF contains an image,
and the image is not rotated or skewed,
and if you want to render that image
with its native resolution, you need a tool for
extracting the image scale.
Ghostscript does not provide such tool,
but someone can implement a new
Ghostscript device driver for extracting that data.

Another way is to patch the PDF interpreter
so that it ignores the image scale,
and render other parts of the document
with no dependence on image size.
It may cause an overlapping of the image with other
text or graphics, so ignoring other objects may be useful.
Currently Ghostscript does not provide
such functionality.

Leo.


----- Original Message ----- 
From: "Barry" <barry at polisource.com>
To: <gs-devel at ghostscript.com>
Sent: Friday, October 19, 2007 10:14 PM
Subject: [gs-devel] Default resolution not properly calculated for rasterpdf 
files


>I use this command to convert a pdf to tiff files:
>
> gswin32c -sOutputFile=PCIE-Report-%03d.tif -r150 -sDEVICE=tiff32nc -dBATCH
> -dNOPAUSE "document.pdf"
>
> But the 150 resolution that's specified in the command is arbitrary. I
> don't know if it's lower or higher than necessary for the best quality
> conversion. If I leave out the resolution setting, the resolution is much
> lower than in the pdf file (the pdf file consists of images of text - it's
> a raster PDF, not vector). The pdf file is a local copy of:
>
> http://democrats.science.house.gov/Media/File/Reports/PCIE%20Report%20on%20NASA%20IG.pdf
>
> When resolution isn't specified in a command that converts a raster pdf
> then the pdf's resolution should be used. If that resolution can be
> determined at the command prompt, I'd like to know how so I can set the
> resolution to the same rather than use the arbitrary resolution of 150.
>
> I posted more detail on this at:
>
> http://studio.imagemagick.org/magick/viewtopic.php?f=1&t=9941
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