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Re: Apple raster, PWG raster and non-free filters/drivers



On Sun 15 Jan 2017 at 22:56:19 -0200, Till Kamppeter wrote:

> On 01/15/2017 04:27 PM, Brian Potkin wrote:
> >
> >Basically, a user needs to know whether the printer will accept PWG
> >raster. From a cursory reading of the Developer Guide for Printers and
> >Connectors at
> >
> >  https://developers.google.com/cloud-print/docs/devguide
> >
> >it would seem that PDF and PWG raster are the formats that a Google
> >Cloud Print Ready printer should accept. I cannot work out whether PDF
> >is the preferred format to send when a printer supports both but (like
> >AirPrint-capable printers having to support Apple raster) it would not
> >be unreasonable to assume PWG raster *has* to be present on the device.
> >PDF does not appear to come with most low-end printers so that makes it
> >likely that all printers claiming to be GCP-compatible would do PWG
> >raster. The Lexmark CS720de does claim this.
> 
> As I understand Google's documentation, the cloud print server queues the
> print jobs in three formats: PDF, PWG Raster, and the unfiltered original.
> The printer is supposed to fetch a job from the queue and it can choose
> which format of the three it takes. This means that the minimum requirements
> for a Cloud Print printer to work are that it understands ONE of the two
> formats PDF and PWG Raster.

After a closer reading of the documentation, particularly

 https://developers.google.com/cloud-print/docs/cdd

it seems there is a hierarchy to the choice for the printer.

  // Section of a CDD that describes the capabilities and physical units of a
  // cloud-connected printer.
  // Content types (sometimes referred to as MIME types) that are supported by
  // the printer.
  //
  // The order of these types determines which content type the document should
  // be converted to. For example, if the types are ordered as:
  //
  //   [
  //     {"content_type": "application/pdf"},
  //     {"content_type": "image/pwg-raster"}
  //   ]
  //
  // Then the document's content type will first be matched to any content type
  // in the list. If there is a match, then the document will be sent to the
  // printer as is. If there is no match, then the document will be converted to
  // a content type which the server supports starting from the first option. In
  // this example, if the document is sent as "text/html" and the printer
  // supports "application/pdf" and "image/pwg-raster", then the document will
  // be converted to "application/pdf" and not "image/pwg-raster", because
  // "application/pdf" is declared earlier in this list.

Later on, it says

  // PWG raster configuration of the printer. Required if the printer supports
  // image/pwg-raster content type, and it should be omitted otherwise.

The word "if" supports your idea of a GCP printer having only to process
one of PDF or PWG raster. The page

 https://developers.google.com/cloud-print/docs/proxyinterfaces

does talk about PWG raster as a fallback to PDF but does not mandate it,
although I suppose a printer manufacturer could choose to provide it in
 addition to PDF for that purpose.

I'm abandoning my contention and moving on to more fruitful things.

-- 
Brian.


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