DPlngScan, or DPscan: see http://www.davidpilling.com/riscos.html
...allows you to set the DPI independently for width and height.
K
--
Kell Gatherer
kell@xxxxxxxxxxxxxxxxx
www.locationworks.com
<http://www.locationworks.com/credits/>
On 23 November 2016 at 15:14, Jim Lesurf <jcgl@xxxxxxxxxxxxxxx> wrote:
Following on from earlier emails about dealing with PDFs I've encountered
something that is new to me, and a bit puzzling...
I've been examining some PDFs from the 'KEF' (loudspeakers) website. One in
particular I'll reference here is the "C_Series_1970.pdf" example linked
from pages like
http://www.kef.com/html/en/explore/about_kef/museum/
1960s/Concerto/index.html
I can use either ArtWorks or PDFutils' pdfimages to extract the jpegs in
this. However the dpi values in them then seem strange.
Both AW and pdfimages give me jpegs with dpi values that are 90 in one
direction and 127 in the other. The images then look squashed.
Setting the dpi values to be the same gives an image that looks OK and
agrees with the rendering of the PDF file. Indeed, showing the images with
something like !NetSurf also makes them look fine as that ignores the
embedded dpi values and just uses 90 dpi regardless.
This raises a couple of questions beyond wondering if anyone else has
enccountered this sort of odd behaviour.
Is this a flaw in the PDF? It seems to have decided to alter one dpi value
and then rescale the rendering to restore the change that would make.
Is there a way to change the dpi values in such jpegs *without* altering
the jpeg data - i.e. to avoid any further loss of image detail? I guess the
dpi values are stored in the jpeg header. But I don't know where. If I did
I could probably hand-edit them. :-)
I can export or convert and set the dpis to be the same, then jpeg the
result. But it means passing the data though another lossy conversion when
the aim here is to get as close to the original as possible.
(Just to clarify. The context is that I'm trying to get KEF to permit us
being able to take copies and keep them for curation as well as for the
Audio Documents public collection.)
Jim
--
Electronics http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.
htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html
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