[NTG-context] shrink JPGs to some resolution (dpi) ?

Harald Koenig koenig at tat.physik.uni-tuebingen.de
Mon Mar 9 22:12:24 CET 2015


so here's my very generic question #1 for my India book:

is it possible that context (lua?) will "shrink" all \externalfigure jpegs
automatically to some specified dpi resolution and quality
(e.g. 300 dpi with 95% jpeg 'quality' for print and
100 dpi and 75% for screen quality) ?

since I'm only using Linux, using Acrobat unfortueately is not an option (thanks, Adobe:-(

that book will be ~100 A4 pages with ~50% and 50% pictures, 
trying to have 2 pictures per page with text flowing around.

the pictures are JPG photos with quite high resolution, upto 24 Mpixel.
so those picutres are HUGE and horrible overkill for a final print
on A4 with typical images withs around 0.5\textwith.

I know about ghostscript being able to convert/shrink PDFs,
but first the "original" PDF with full size JPGs with be really huge,
and ghostscript takes ages to shrink them.  so that's not real fun 
doing this too often...

right now I write the real typeset size of all images to the log file
and use some external script to calculate the current resolution
and then create a new set of images which e.g. 300 dpi.

but that's still an ugly hack still has some issues with EXIF data, rotation, clipping, ...
and right now leads to strage problems (see mext mail;)

any hints to read the original large JPGs, but only write "print quality" 300dpi images,
or low quaity 75dpi images for speed (and saving net bandwidth when mailing PDFs
to co-workers of the group)?


"I hope to die                                      ___       _____
before I *have* to use Microsoft Word.",           0--,|    /OOOOOOO\
Donald E. Knuth, 02-Oct-2001 in Tuebingen.        <_/  /  /OOOOOOOOOOO\
                                                    \  \/OOOOOOOOOOOOOOO\
                                                      \ OOOOOOOOOOOOOOOOO|//
Harald Koenig                                           //  /     \\  \
koenig at tat.physik.uni-tuebingen.de                     ^^^^^       ^^^^^

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