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OpenPrinting GitHub

Code License: See project descriptions

The participation of the Linux Foundation in the Google Summer of Code is organized by Till Kamppeter (till at linux dot com) and Aveek Basu (basu dot aveek at gmail dot com).

Classic printer drivers for CUPS-based printing environment consist of print filters which convert a known page data format (like CUPS/PWG Raster, PostScript, PDF, …) into the printer's native data format and PPD (PostScript Printer Description) files which describe the printer's capabilities, user-settable options, and the way how the print filters are used.

The PPD files and print filters have to be put into standardized directories of the installed CUPS system so that CUPS finds them and allows the selection of this printer driver when setting up a printer (or selects the driver automatically when identifying a printer as supported).

This method works well in standard desktop and server systems using RPM or Debian packages and when the source code of the driver's filters is available or the driver is packaged for the operating system distribution in use. If the CUPS environment is provided in a sandboxed package like this Snap adding files to the CUPS installation is not possible, and in addition, one wants to provide the drivers in distribution-independent binary packages, as for example Snaps. Also the CUPS project is deprecating the use of PPD files.

The solution, suggested by Michael Sweet, the author of CUPS, are Printer Applications. Printer Applications are simple daemons which emulate a driverless IPP network printer on localhost, do the conversion of the print jobs into the printer's format, and send the job off to the printer. And as a physical driverless IPP printer they advertise themselves via DNS-SD and provide there capability information on (IPP) request from the client.

The IP connection between CUPS and the Printer Application allows both being in different sandboxes (for example being installed from different Snap packages) and the printer setup is completely automatic. When the Printer Application's daemon is running and the printer is connected and turned on, the daemon discovers the printer and automatically advertises it on the local machine via DNS-SD. Then CUPS discovers the printer and automatically sets up a print queue with an auto-generated PPD file.

The student's tasks here are

• Create a universal printer application framework which can be packaged with print filters and PPDs to make up a Printer Application
• Use this framework to create Printer Applications for drivers like HPLIP, foo2zjs, Gutenprint, SpliX, …
• Use this framework to make a Printer Application for Foomatic
• Making Snaps of Printer Applications.

Existing free software which could be used to accomplish this task are CUPS/libcups, PWG's ippsample, cups-filters, Ghostscript, MuPDF, …

The tasks can be distributed to more than one student if needed.

Mentors: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), TBD

Desired knowledge: C programming, DNS-SD, IPP

Code License: Apache 2.0, MIT

The Internet Printing Protocol (IPP) does not only support printing, but also scanning, as there are many printers which also have a scanner (multi-function (MF) devices). Both CUPS and the developer tool ippserver emulate IPP network printers but not IPP scanners and so they cannot serve as a server to share a local scanner.

This task is about adding the scan server functionality. If you have a scanner connected locally (and it scans via SANE), share it as an IPP scanner, advertising itself and accepting jobs using the IPP driverless scanning standard. In contrary to SANE-based network scanning clients with any operating system, also phones or IoT devices can scan on your shared scanner.

Also old hardware can be recycled to a modern MF device, and we have a sample implementation to motivate manufacturers to adopt IPP scanning.

This server software will be a so-called Scanner Application, a sample implementation of the future form of scanner drivers, easily packageable in sandboxed, distribution-independent package formats like Snap.

Mentors: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), SANE upstream developers TBD

Desired knowledge: C programming, DNS-SD, IPP

Code License: Apache 2.0

Version 2.0 and newer of the Internet Printing Protocol (IPP) support polling the full set of capabilities of a printer and if the printer supports a known Page Description Language (PDL), like PWG Raster, Apple Raster, PCLm, or PDF, it is possible to print without printer-model-specific software (driver) or data (PPD file), so-called “driverless” printing. This concept was introduced for printing from smartphones and IoT devices which do not hold a large collection of printer drivers. Driverless printing is already fully supported under Linux. Standards following this scheme are IPP Everwhere, Apple AirPrint, Mopria, and Wi-Fi Direct Print.

As there are many multi-function devices (printer/scanner/copier all-in-one) which use the IPP, the Printing Working Group (PWG) has also worked out a standard for IPP-based scanning, “driverless” scanning, to also allow scanning from a wide range of client devices, independent of which operating systems they are running.

Conventional scanners are supported under Linux via the SANE (Scanner Access Now Easy) system and require drivers specific to the different scanner models. Most of them are written based on reverse-engineering due to lack of support by the scanner manufacturers. To get driverless scanning working with the software the users are used to the best solution is to write a SANE module for driverless IPP scanning. This module will then automatically support all IPP scanners, thousands of scanners where many of them do not yet exist.

Even if there are no driverless IPP scanners on the market yet, this module can be used for accessing scanners with their driver provided as Scanner Application (see previous project in this list).

The student's task is to write this SANE module for IPP driverless scanning and so make Linux ready for the future of driverless devices.

Mentors: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), SANE upstream developers TBD

Desired knowledge: C programming, DNS-SD, IPP

Code license: GPL 2+

ipptool is a command line tool for issuing IPP requests and receiving printer's/server's responses. ipptool is maintained as free software in the ippsample collection from the IEEE-ISTO Printer Working Group (PWG). ipptool is used for development and debugging of IPP-related software and for PWG self-certification for IPP Everywhere printers for driverless printing.

The student's task is to develop additional ipptool test scripts for all new operations, objects, attributes defined in IPP System Service v1.0 (e.g., Create-Printer).

Mentors: Ira McDonald (blueroofmusic at gmail dot com), Printing Working Group, Smith Kennedy (smith dot kennedy at hp dot com), HP, TBD

Desired knowledge: C programming, IPP

Code License: Apache 2.0

ipptool is a command line tool for issuing IPP requests and receiving printer's/server's responses. ipptool is maintained as free software in the ippsample collection from the IEEE-ISTO Printer Working Group (PWG). ipptool is used for development and debugging of IPP-related software and for PWG self-certification for IPP Everywhere printers for driverless printing.

The student's task is to develop additional ipptool test scripts for IPP errata including IPP Document Object v1.1, IPP Job Extensions v1.1, and IPP 3D Printing Extensions v1.1.

Mentors: Ira McDonald (blueroofmusic at gmail dot com), Printing Working Group, Smith Kennedy (smith dot kennedy at hp dot com), HP, TBD

Desired knowledge: C programming, IPP

Code License: Apache 2.0

Most network printers have a web interface which allows to configure the printer from any computer in the network using a web browser. Advantage is that no printer-model-specific software needs to be installed on the computer in order to configure a printer, and one has no dependency on certain supported operating systems. One can even configure printers using a smartphone.

Disadvantage is that every manufacturer does its web interface differently which makes administration of many printers of different brands awkward. In addition, automated printer administration with scripts requires different interfaces for each printer. And for setting local print queues you open your printer setup tool but for printer administration you have to open your browser.

To make this easier the Printing Working Group (PWG) has introduced the IPP System Service standard. This is an interface made up of standardized IPP requests to poll printer capabilities and configure the printer as needed. Every printer from every manufacturer uses the same requests and so a common printer configuration interface can be added to printer setup tools or automated administration with scripts is possible.

The student's task will be to create an appropriate printer configuration interface for system-config-printer or for the GNOME Control Center.

Mentors: Upstream developers of GNOME/GTK or system-config-printer TBD.

Desired knowledge: C and/or Python programming, GTK

Code License: GPL 2+ or LGPL 2+

The cups-filters project at OpenPrinting (included in all Linux distributions using CUPS 1.6.x or newer) provides the filters needed to convert the print job output of desktop applications (usually PDF) into the printer's native language or into the universal CUPS/PWG-Raster format as input for a separate printer driver. It also provides the pdftopdf filter to apply page management (N pages per sheet, selected pages, even/odd pages for manual duplex, mirror for iron-on sheets, …) to the PDF data stream.

One of the filters, pdftoraster, to rasterize PDF files into CUPS/PWG Raster, uses Poppler but makes use of unstable APIs of Poppler, requiring frequent modifications when Poppler gets updated.

The task for the student is here to improve pdftoraster's interface with Poppler, for example using Poppler's PPM (generic raster) output and converting it into CUPS/PWG Raster. Discussion about possible approaches you can find on the cups-filters GitHub.

Mentors: Sahil Arora (sahilarora dot 535 at gmail dot com), Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), Tobias Hoffmann, cups-filters developer (smilingthax at googlemail dot com).

Desired knowledge: C and/or C++ programming

Code License: MIT

CUPS has two mechanisms for on-the-fly-PPD generation to avoid the wasting of disk space by thousands of uncompressed (or slightly compressed) PPD files. One is to put an executable file into the /usr/lib/cups/driver/ directory which lists and generates PPD files on request, the other is using *.drv files in /usr/share/cups/drv, which contain the data for the PPDs in a simpler and more compact format.

The former method is deprecated upstream and can be removed in a future release of CUPS, especially also because the executables can get slow in some cases.

The latter is not yet supported by Foomatic and letting Foomatic support it is subject of this project idea.

The student's task is to create a utility which generates *.drv files from the whole database and/or from selected, printers, manufacturers, drivers, groups, …, depending on what the user requests.

Mentor: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com)

Desired knowledge: Perl programming, perhaps also MySQL

Code License: GPL

MuPDF is a lightweight PDF renderer made by Artifex, the company behind Ghostscript. In contrary to Ghostscript, MuPDF is a pure PDF renderer. It does not contain a PostScript interpreter nor parts of it are written in PostScript. This makes it smaller, faster, and less resource-consuming, the ideal solution for mobile devices like tablets or smartphones.

On mobile devices printing will not be done with having tons of printer-model-specific drivers on the system. Once, they consume the limited mass storage space, and second, one uses the mobile device in several different local networks with different printers: At home, in the office, in a copy shop, … and one wants to use the printers which are available there, without installing drivers and setting up queues.

Therefore we want to have a system which automatically detects network printers and makes them available for local apps. To do so we restrict ourselves to printers with known, common languages: IPP Everywhere/AirPrint/Mopria/W-Fi Direct (driverless printing standards, using PWG Raster, Apple Raster, PCLm, and PDF) and PostScript, PDF, PCL 5c/e/6/XL (legacy standards). So MuPDF has to generate raster output for these languages, meaning raster embedded in the specifics of the language, and to avoid exhausting printer resources raster in small bands and no high-level output, even if the printer language is high-level.

Artifex will also work on this, but to get additional man power we are also opening this project for students.

Note that you have to assign copyright on your code to Artifex, as otherwise the code cannot be integrated in MuPDF.

This project can be split to be worked on by more than one student.

Mentors: MuPDF developers TBD, Till Kamppeter, Project Leader OpenPrinting (till at linux dot com)

Desired knowledge: C and/or C++ programming

Code License: GPL

The Qt Print Support framework should be updated with the CPD support. The goal is to provide the CPD GUI features and d-bus communications with the CPD backend support for printing from Qt5 applications on support platforms.

Based on the GSoC work of the previous year, one example of Qt CPD implementation outside of Qt Print Support can be found at: https://github.com/rithvikp1998/CPDv2. For this task, the implementation is expected to start with QPrintDialog instead.

Mentors: Dongxu Li (dongxuli2011 at gmail dot com), Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), TBD

Desired knowledge: C++ programming, Qt, CUPS

Licenses: Qt Contribution Agreement

system-config-printer was the default printer setup tool in Red Hat/Fedora Linux for a lot of time and also got adopted by Ubuntu around ten years ago. During this time it received a lot of development work, especially on the algorithms for finding the best driver for a printer and for identifying whether printer discovery results from the CUPS backends actually come from the same physical printer.

To make these algorithms available for other printer setup tools (both interactive GUI tools and programs which fully automatically create print queues without user interaction) they got moved into a D-Bus service, scp-dbus-service. Now every other program can simply call the needed function via a D-Bus API. The printer setup tool in the GNOME Control Center for example works this way.

system-config-printer was written in Python and therefore scp-dbus-service is also written in Python. This makes it depending on Python and also makes it loading the needed Python libraries into memory when started. This can cause delays during boot when a utility to auto-setup print queues is used.Also most printer setup tools are written in C, Therefore it makes sense to convert the D-Bus service into the C language.

The student's task is to turn the scp-dbus-service of system-config-printer into C, either as D-Bus service (would work out-of-the-box with many GUIs) or as a C library with API (simpler), ideally both. This will make it easier to write printer setup tools in practically any programming language.

Mentors: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), system-config-printer upstream developers TBD

Desired knowledge: C/C++ programming, Python programming

Code license: GPL 2+ or MIT

Google Cloud Print is a service from Google which allows to print from anywhere with internet access to anywhere else with internet access, for example from a mobile phone to printer at home or in the office.

To do so, one needs a Google account and there one registers one's printers so that they can accept jobs sent into the print facility of this Google account.

On Linux there is already a way to share the local CUPS printers into Cloud Print: The Chrome/Chromium Browser. In its settings you can activate Google Cloud Print and the local queues get registered. The Browser even leaves a user daemon running when one closes it to continue keeping the printers available for Cloud Print.

The disadvantage of this is that the functionality is bound to a web browser, so it is awkward for people who use Firefox for example.

Do not suggest now to make the CUPS daemon (daemon which handles the print jobs) or cups-browsed (daemon which browses the network for printers and automatically creates local queues for them) registering the printers, as they are system-wide services and Google Cloud Print is based on the user's Google account, and so something which belongs to a single user.

What is needed is a user daemon which starts when logging in and stops when logging out, running with the rights of the user, connecting to the user's Google account registering the local CUPS printers the user is allowed to print on. It will need integration with the desktop for starting and stopping the daemon and for configuration in the desktop's settings utility.

Ideally it should work with the GNOME desktop using GNOME Online Accounts and the GNOME settings manager.

Google documentation for printer registration.

Mentors: Till Kamppeter, Project Leader OpenPrinting (till at linux dot com), Ubuntu/GNOME GUI developers TBD

Desired knowledge: C/C++ programming, GUI programming, GTK

Sometimes you browse through your files and see some files which you want to print, files in completely different formats: PDFs, photos, LibreOffice files, … It is awkward to double-click each file, one-by-one, to get it opened in its application, and then click “Print” in each application. It would be much easier to mark all these files, right-click and then click “Print” in the context menu.

Here the student's task is to add this functionality to a popular file manager, for example the one of GNOME.

Mentors: Aveek Basu (basu dot aveek at gmail dot com), upstream developers of GNOME/GTK TBD.

Desired knowledge: C programming, GTK

Code License: LGPL 2+

Adrian Johnson did a lot of the work needed to make cairo color managed. Finishing this work and getting the code upstream would allow us to simplify a lot of applications that use cairo. See http://cgit.freedesktop.org/~ajohnson/cairo/log/?h=color-space for the branch. Adrian has also patched Inkscape to use the new features, and that needs cleaning up and pushing upstream http://cgit.freedesktop.org/~ajohnson/inkscape/log/?h=color-space Also see http://lists.cairographics.org/archives/cairo/2012-July/023353.html and https://mail.gnome.org/archives/gimp-developer-list/2012-August/msg00084.html for more details.

Expectations: The cairo and inskcape code is pushed upstream with any required modifications. Ideally someone familiar with the cairo community would take this on, as Adrian found it hard to get the code approved upstream.

Skills: Understanding of basic color management, basic use of bzr and git, proficient in C.

Contact: Richard Hughes (hughsient at gmail dot com)