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

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


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.

PDL-wise this is good enough for driverless printing with CUPS and cups-filters, as we can generate both PDF and PWG Raster.

In addition, for driverless printing a printer needs to support IPP 2.0 (so that we can poll the printer's capabilities to generate a PPD file) and Bonjour (so that we can discover the printer in the local network).

The Cloud Print documentation does not talk about the use of IPP and Bonjour, which gives me the impression that there can be printers marketed as GCP-compatible but do not support IPP 2.0 and/or Bonjour.

Unless a manufacturer takes the time and trouble to self-certify a
printer for IPP Everywhere use there is no way of knowing how much of
IPP it supports without trying it. But, thinking on, printouts should be
reasonablely good if the manufacturer has done a good job for GCP.

That is my contention, then. You can be confident "GCP Ready" gets you
PWG raster on the printer. And this can be known beforehand.

Note that we also need to assure that the printer supports IPP 2.0 and Bonjour for driverless printing.

In general, we do not need to distinguish between AirPrint, IPP Everywhere, ... but simply say driverless printing and this requires:

1. Printer is a network printer which advertises itself via Bonjour OR printer is a USB printer which does IPP-over-USB.

2. Printer supports IPP 2.0 or a newer IPP version

3. Printer understands at least one of the following PDLs:

   - PWG Raster
   - Apple Raster
   - PDF

With this fulfilled we can print driverless with CUPS, cups-filters and one of Ghostscript, Poppler, or MuPDF. For network printers we need avahi-daemon in addition, for USB printers ippusbxd.


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