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.
