[XeTeX] XeTeX, XeTeXpicfile, and transparency

[Zdenek Wagner]

2012/3/16 Philip TAYLOR <P.Taylor at rhul.ac.uk>:
>
>
> Peter Dyballa wrote:
>>
>>
>> Am 16.3.2012 um 14:28 schrieb Philip TAYLOR:
>>
>>> Universe of Discourse : Plain XeTeX (as stated previously).
>>
>>
>> I don't know what this is meant to express,
>
>
> That I use XeTeX; I do not use XeLaTeX, ConTeXt or any other
> higher-level interface.  I use the raw engine, with Knuth's
> plain format, and thus any solution that is predicated on the
> use of (e.g.,) "fontspec", "LaTeX", "XeLaTeX", "ConTeXt", and
> so on, cannot be of use to me in my quest.
>
>
>> It's also possible to prepare the image that it itself becomes
>> transparent.
>
>
> Yes, I have been experimenting with this, but a native
> (XeTeX) solution would be preferable ...
>
There are two separate problems:

1. Prepare an image with transparency. You must use a format supporting it

2. Include the picture an a way preserving transparency. When doing
this you must ensure that you create a PDF with a minor version
supporting transparency. If the version does not support transparency,
then it is an expected behaviour that xdvipdfmx will remove it.
Remember that transparency is explicitely prohibited in PDF/X and
PDF/A. I do not know the first version of PDF supporting transparency
Default of xdvipdfmx is 1.4 but can be changed by -V.
>
>> Another option is to insert the picture transparently as the
>> background. The pdfTeX engine supports this via a few LaTeX
>> packages.
>
>
> That would be useful, were it it not for the dependency
> on LaTeX and LaTeX packages.
>
Image inclusion in pdftex can be achieved by pdftex primitives (if I
remember it well, by \pdfximage etc). LaTeX packages do nothing but
provide macros calling these primitives. It is not difficult to find
their description. the note concerning the PDF version still applies,
transparency will be removed if the minor version is not high enough.
The difference is that the minor version can be both queried and set
via \pdfminorversion and most probably the default is set so that the
transparency is supported.

The plain pdftex commands for using transparent text are given in
Czech in one article in the CSTUG Zpravodaj.

> ** Phil.
>
>
>
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-- 
Zdeněk Wagner
http://hroch486.icpf.cas.cz/wagner/
http://icebearsoft.euweb.cz