[pdftex] proper jpeg inclusion

Jiri Osoba osoba at jablotron.cz
Wed Feb 26 10:25:56 CET 2003


JPEG is included AS-IS - you can find identical bitstreams in JPG and PDF.
PDFTeX reads dimensions from JPG and sets the transformation matrix in PDF.
And then copies whole JPG file into PDF without touching any byte.


> ----- Original Message -----
> From: Peter Fischer
> To: pdftex at tug.org
> Sent: Wednesday, February 26, 2003 1:37 AM
> Subject: [pdftex] proper jpeg inclusion
> Hi out there!
> I noticed that the jpeg images I include look worse than the originals
> (less colors). I use pdflatex, the graphicx package with
> and acrobat reader to display the result. I can exclude that the reasons
> the graphics card or the display I use because they work at 32 bit/pixel
> and 1280x1024 pixel respectively.
> I've also checked this without rescaling, i.e. included the images in
> their original sizes so no rerastering/recompressing should be done by
> pdflatex.
> I suspect that acrobat performs some filtering but I wanted to be safe
> there aren't any parameters of pdflatex or graphicx I am not aware of.
> As far as I have figured out \pdfcompresslevel is deactivated per default
> and only uses lossless zlib-compression anyway.
> Furthermore I have found this thread where it is stated that pdftex
> isn't able and therefore doesn't perform any jpeg reencoding:
> http://tug.org/mailman/htdig/pdftex/2001-August/001463.html
> So please help: How can I make my jpegs look exactly the same
> in the pdf like in the original file?
> Can I be definitely sure that there really is no quality loss when using
> pdflatex/graphicx?
> Thank you for helping me and have a nice day!
> Peter Fischer.
> --------------------------------------------------------------------
> Peter Fischer
> Universitaet Karlsruhe
> Fakultaet fuer Informatik
> Institut fuer Betriebs- und Dialogsysteme
> Am Fasanengarten 5
> 76128 Karlsruhe
> E-mail: pfischer at ira.uka.de
> --------------------------------------------------------------------

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