[cups.development] pdf with transparent image and cups raster filter

[bowhe casia]

Your PDF might be containing multiple layers of transparency beyond the reach of cups to convert it to raster. The number of layers depend on the application that generates it.

To verify this, try to open your PDF file on a Mac machine and print-save it as PDF. After that, you print the generated PDF using your raster driver. Mac normally flattens the PDF transparency layers to a level that can be reached by cups.



--- On Fri, 6/11/10, Paul Newall <p.newalls at ntlworld.com> wrote:

> From: Paul Newall <p.newalls at ntlworld.com>
> Subject: [cups.development] pdf with transparent image and cups raster filter
> To: cups-dev at easysw.com
> Date: Friday, June 11, 2010, 1:36 AM
> I have a cups raster filter, using
> colorspace CUPS_CSPACE_K or CUPS_CSPACE_CMYK
> Some pdf files fail to print.  The common factor seems
> to be that they contain an image with some transparency.
> The filter is behaving as though the raster was blank
> (every byte of the data = 0). It's possible that there's
> some problem with the filter, but before I spend a lot of
> time looking at that...
> Are there any known problems with cups converting pdfs with
> transparency to raster format?
> Any ideas for how I should investigate this?
> Maybe the pdf files are not to specification in some way?
> Is there a pdf file validity check I can run? or are there
> sample "correct" pdf files somewhere I can download? Or
> sample postscript files with transparency that I can use to
> see if the problem applies only to pdfs?
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