[Scribus] transparency question

jon info
Tue May 15 18:58:15 CEST 2007

> avox schrieb am Montag, 14. Mai 2007:
>> jrm wrote:
>>> Hi,
>>> This regards using png images with portions that are
>>> 100% transparent.  What seems to happen is that this
>>> kind of transparency is respected even when exporting
>>> to PDF 1.3 (as seen in acroread and kpdf), which is not
>>> what I was expecting.  So I'm wondering if this is
>>> too good to be true, that I may be able to use this
>>> kind of transparency without restriction on what PDF
>>> version to use, maybe even PDF/X-3...  The question is,
>>> can I rely on this behaviour?
>>> What I guess was expecting was that since "PDF 1.3 does
>>> not allow transparency" the transparent part of the png
>>> would be made white, or maybe black.
>> AFAIK PDF has supported hard masks for images from the beginning
>> (that's also possible in PostScript using the imagemask operator).
>> What is only possible since 1.4 is softmasks (alpha channel), since
>> those require blending imagepixels with background pixels.
>> I don't know if the behaviour for images with an alpha channel which
>> contains only 0% and 100% values is defined, better not rely on that.
>> Using an indexed palette with a special color for 'transparent'  
>> should
>> work.
> Hi,
> Though I don't know the standard, I got my X3 PDf printed corrctly,  
> when using
> 100% transparency in PNG and tiffs.
> This always seems to work, I use this bug/feature (?) every month,  
> when I make
> a flyer.

Hi Jan, are you using bitmaps for masking? Or rgb/grayscale images  
with alpha or indexed transparencies?
How are the flyers printed (digiprint or ctp)?

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