For a few weeks now, the OTB development team has been working on this task called refactoring. In software development, the purpose of refactoring is to rewrite parts of the code to enhance its robustness and clarity, to make it easier to maintain and re-usable in other contexts, without modifying its external functional behaviour (source: wikipedia). That is why end users should not notice a lot of changes appart from minor changes in the way it looks. But behind the curtains, it makes a big difference.

The whole visualization module is now fully compliant with the Model-View-Controller architecture in use in the most recent OTB applications. The initial limited set of classes has been splitted into several lighter classes and customization entry points have been carefully introduced in each critical part in order to provide maximum extensibility at minimal cost. Adding a new user interaction, a new type of curve to display or a new eyecandy object rendering onto the image is now as simple as rewriting a light class with about no code overhead.

The otbFeatureExtractionApplication was chosen to beta-test the refactored module, and was therefore modified to use the new visualization tool. Migrating the applications essentially involved removing hundreds of lines of code without compromising any of its functions, and therefore greatly improved its clarity, robustness and maintainabilty. We are already on the way to migrate other applications in order to make everyone benefit from the changes.

The otbFeatureExtractionApplication now uses the new visualization module

Using the new design, we also built a new overlay component to render the content of a shapefile or a kml file over an image in about no time.

Using the new design, a tool to quickly render vector data files (shapefile or kml) has been built

Of course, this does not extend the functionnal scope of the Orfeo ToolBox or its applications, but in the future, it will help us to reduce the cost and improve the robustness of new applications. Developping users will also find it easier to extend it to suit their needs. For further technical details, you might want to read the OTB wiki page on this topic, which includes a small tutorial to start using the new visualization module.

The application has been redesigned from scratch and will be distributed with the next release of OTB (2.8) coming next Monday. You can now load full images, as only the area displayed will be processed. You also have access to all the parameters (you can refer to the ICIP paper for details: E. Christophe, J. Inglada, Robust Road Extraction for High Resolution Satellite Images, ICIP 2007).

Road Extraction Application

One of the main improvement is coming from the changes in the vector data handling. Now, OTB knows how to convert these data between different projection systems (which could be map projections or sensor models). That means that you can now export the results of the main OTB application in shapefile format to load it in you favorite GIS (Quantum GIS for example) or in KML to load it in Google Earth.

For example, with the previous extraction, Google Earth will display:

Road extraction results on Google Earth

You can notice that there is an offset of several meters due to registration problems. Indeed the orthorectification of the image used for the extraction was not done with OTB and images on Google Earth can also suffer from registration problems.

Looking as such results may give you some ideas of new stuff to try with OTB. We are bubbling with ideas but lacking the time to try them all!

One last thing, the algorithm included here is far from being perfect and was designed mostly to be fast enough to allow interaction. There are many ways to improve the results and adapt the algorithm to your needs. The good thing is that this application has been designed following the MVC architecture. That means that the visualization (the View) is decoupled from the processing (the Model). You could quite easily create a new model with a completely different algorithm to have a better road extraction application. Feel free to reuse the code!