[cups.general] Filer order.

Michael Sweet msweet at apple.com
Fri Sep 18 16:34:10 PDT 2009


On Sep 18, 2009, at 2:11 PM, Dyna wrote:
> Hi,
>
> I tried to figure out what order a particular driver executes  
> filters (the once down in lib/cups/filter). If I in a ppd add a  
> filter say (its the only filter in the ppd -- the ppd is for a HP  
> 8550 via hpijs) :
>
> *cupsFilter: "application/vnd.cups-postscript 0 toGray"
>
> Well it does execute the filter but not first and surly not last  
> either (or at least it doesn't look like it).

It generally will be the last filter before the backend; the only  
possible filter between it and the backend would be the port monitor  
which has to be explicitly configured.

> It's in the middle along a string of filters that the driver uses.  
> However I can't find where the order or the filters are actually  
> defined. Maybe I'm out dreaming in the blue sky ;) but it would be  
> good to know where I could start looking at least.... I want my  
> filter to be executed first as a prefilter on the incoming  
> Postscript or just after a filter producing the first postscript if  
> we for example print a text file.


If you want to be the first filter for a format, use the cupsPreFilter  
keyword in the PPD file.

The order of filters is defined by their input and output formats,  
along with the source and destination formats.  For example, if you  
print a PDF file on Linux to a printer with your PPD file, you'd see  
the following filters get run:

     pdftops | pstops | toGray | backend

___________________________________________________
Michael Sweet, Senior Printing System Engineer







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