[pdftex] Image transparency

George N. White III WhiteG at mar.dfo-mpo.gc.ca
Thu Jun 21 11:42:15 CEST 2001

On Thu, 21 Jun 2001, Hans Hagen wrote:

> are there better png libraries than the one currently used in pdftex?

I don't think pdftex uses everything the libraries can do, but I'm
not sure we want the added complexity in pdftex.

> >Rather than trying to improve support for images in pdftex I would
> >prefer to see better tools to generate PDF files with images that
> >can be placed into pdftex documents.  It is useful to have the
> >current basic PNG support for less demanding applications, but
> >it would be difficult to provide access to the full image capabilities
> >of PDF from pdeftex, and these capabilities are likely to change in
> >the future to support things like JPEG 2000.
> the number of compression schemes in pdf is not that large so it should be
> possible to develop a decent set of filters, how good is the free stuff
> that cna be used for that? Is there for instance real good [complete] and
> free tiff->pdf conversion available?

It was been a while since I looked into this.  There are lots of
free image-->EPS tools, but very few support indexed color (most convert
everything to RGB).  I think ImageMagick was the exception.  In principle,
it would not be hard to modify these tools to generate PDF, and in fact
I would be surprised if ImageMagick and Gimp don't have some direct
PDF capabilities by now, but I would also be surprised if these don't
need considerable tweaking to support PNG's gamma, etc.

Since I want to mimic Photoshop EPS + distiller's color handling, it will
be easier for me to first get EPS that looks like Photoshop EPS and then
(get someone else to) make ghostscript's pdfwrite device do the right
thing.  I think the latter is pretty well in hand already.

George N. White III <gnw3 at acm.org> Bedford Institute of Oceanography

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