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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