digiKam: Web Services tools authentication with OAuth2

digiKam is a desktop application for photos management. digiKam provides a wide range of plugins for exporting photos to web services (e.g dropbox, flickr, facebook, etc.) alowing users to easily upload their photos to cloud storage services or share photos on social networks.

Current export tool authentication process makes it far from easy-to-use for users. In addition, authentication protocols varies much for each web service, generating many difficulties for implementation and code maintaining. Hence, this project is aimed to resolve those problems by porting authentication flow with O2 library, in order to make digiKam export tool more user-friendly and more flexible for development and maintenance.

Mentors : Maik Qualmann, Gilles Caulier

Project Goals

  • Port export plugins with O2 library.
  • Factor codes of new wizard for export plugins.
  • Accomplish new wizard with features for photo processing before uploading.

Work report

Coding period : Phase one (May 14th to June 15th)

This phase is to port 3 digiKam web services : Google, Facebook and Smugmug to O2. It is required to change the authentication flow but still preserve main functionalities. In general, work for this part is nearly done, except some minor existant bugs to be resolved.

Google photo.png

According to my initial plan, I must also have finished Youtube Uploader by this time. However, since porting these web services to O2 is more important and Youtube Uploader can be finished in phase two of project, when i will be working on code factorization for other web services, the whole first part of project was then spent on porting to O2.

Below is my project status.


Resolved :

  • Authentication with OAuth2
  • All methods are ported to new APIs (v2)
  • Anonymous mode is removed
Google Drive

Resolved :

  • Authentication with OAuth2
  • Export is ported to keep compatibility with O2
Google Photo

Resolved :

  • Authentication with OAuth2
  • All methods are ported to Google Photo APIs (to replace current methods based on Picasa APIs)

Unresolved :

  • Photos import from Google Photo are not visualized in digiKam
  • Cannot export to albums not created by digiKam (lack of authorization scope from Google Photo APIs)

Resolved :

  • Authentication with OAuth2
  • All methods are ported to new API (v3) and kept compatibility with O2

Unresolved :

  • Cannot create album by digiKam
  • App review to put digiKam public mode

Coding period : Phase two (June 15th to July 13th)

In this phase, I continue working on each web service separately to fix bugs and prepare for beta release of digiKam 6.0.0. Moreover, the main part of this phase is factoring codes for web services.

Concretely, factoring is divided in two parts: authentication flow, and export tool GUI. It has to be mentioned that Gilles Caulier, one of my mentors, has prepared a common wizard for export tool. Thus, I took it as base ground to develop new export GUI.

Centralized authentication flow

Indeed, OAuth2 (or even OAuth 1.0) implementation for web services in digiKam is highly redundant, especially in talker.cpp, because the authentication flow is the same and has to follow the protocol for security reason. However, implementing OAuth2 in each web service makes codes' become less clear, as well as requires much more efforts for scaling and maintaining.

To resolve that problem, the idea is to define a base class for all web services, where we group all common codes, especially for authentication. Currently in digiKam, web service talker is the class handling all communication between digiKam and web service for access token exchange, API calls, as well as API responses processing. Hence, a base class (wstalker) for all talkers is appropriate to define the standard authentication flow and API exchanges between digiKam and web service.

Methods to control the flow, API calls and parsing API responses in wstalker are virtual and will be reimplemented in each web service talker, depending on API specifications.

Common UI for export tool

The solution is very similar to the case of authentication flow. I decided to create a base class containing necessary signals and slots in common between all web services.

Besides, I also worked on this part at the same time with authentication flow fafctoring, so that I can have a GUI to test. Here are some screen shots of what I have integrated to the common wizard for export tool

New intropage.png


New wizard facebook1.png

New wizard facebook3.png

Coding period : Phase three (July14th to August 6th)

After phase two, discussing with my mentors about the importance of code factoring for web services, we finally all agreed that code factoring is still the most important task to finish at the moment. In later releases of digiKam, we look forwards to replacing the current long list of web services to export to put all of them into a common wizard. Thus, I continue working on code factoring and developing that wizard in the third stage of GSoC 2018.

Centralized authentication flow (continue)

As the structure for web service talker has been established in phase two, task for phase three is completing more and more that structure, as well as adapt it to the new GUI. Below is a simplified diagram of talkers' structure.

Auth talkers structure.png

Technically, wstalker (base class for talkers) is only designed for web services that can be ported with O2 at present. Other web services have their own ways for authentication via REST API, so they cannot be implemented as a derived class of wstalker. . At that time, idea of a base class asand wstalker will then be

Important Links

Proposal Link

Project Proposal

Git dev branch



Email: [email protected]

Github: TrungDinhT

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