[Samba] Re: CUPS Print Quality -- WAS -- UPDATE Where are the ADOBE PS Drivers?

[Simon Hobson]

Chris McKeever wrote:

>  > I would guess that there is probably at least some quality lost during
>>  that conversion and the resulting output would depend entirely on
>>  ghostscript's ability to translate (render) the Postscript generated by
>>  the driver on Windows into your printer's native tongue.
>
>yeah - I am thinking this is the issue...

There shouldn't be - see below

>  > If you didn't need to do the PS->(some other language) conversion on the
>>  CUPS server then I suspect you would see better resulting output.
>>  Trying to avoid this PS->(other) conversion step is one of the reasons
>>  why I generally only support PS capable printers.  You might want to
>>  look into adding Postscript support to your printers if it is available
>>  as an add-on option (assuming you don't want to continue to just use
>>  CUPS in raw mode - there really isn't anything "wrong" with that, it's
>>  just not how I'd like to have my system setup).
>>
>
>Can I ask a really basic question, that may help me get my hands
>around this stuff...On the windows side the application prints using
>the ADOBE (or whatever) Driver and the vendor specific PPD file.  It
>then gets sent to cups which then does what??  Does the CUPS server
>process it again before sending to the printer (assuming the printer
>is postscript capable)?
>
>The reason I ask, was that I thought (for some reason) that the CUPS
>processing made the windows client driver independent - but if the
>windows client uses the PPD - then I am thinking that I was mistaken

It's fairly well described in the Samba Howto IIRC. To paraphrase ...

If configured for raw printing then it simply passes whatever it is 
given on to the output stream. Otherwise ...

The first step (as far as Samba printing is concerned), if not 
already feeding it the right format, is to pre-process the input file 
to extract device specific options and convert them to Cups 
parameters and generate a device-independent Postscript file.

It selects a set of conversion filters, typically using Ghostscript 
to generate a bitmap image and then encode this into the printers 
native format.

Once the job is in a format the printer can understand, it is sent 
through the configured output device/transport to the printer.


If properly configured, there is no reason that Cups should not be 
able to produce output as good as any other driver. The quality you 
actually get will largely depend on the settings (particularly 
resolution and colour depth) for the PS to bitmap conversion, plus an 
element of how well the device dependent filter converts the 
resulting bitmap to the printers native format.


 From the above, you can prbably imagine that if you use a generic 
PPD, you can use the same driver and PPD for all printers, but you 
won't get access to all the facilities available on a printer. If you 
stick with the Adobe PS drivers, then you can use the same driver for 
all printers, only the PPD is different.


Simon

-- 
Simon Hobson MA MIEE, Technology Specialist
Colony Gift Corporation Limited
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