Rectilinear to equirectangular_v0.1 - FoxelSA/libgnomonic GitHub Wiki

The rectilinear to equirectangular mapping projection functions allow to reproject a rectilinear mapping back into the equirectangular mapping. This functionality is especially useful for edition of equirectangular projected panorama. It provides the possibility to edit such mapping working on rectilinear mapping that remove distortions appearing on panorama due to their specific representation.

To illustrate the functionality offered by the library, we consider the following entire equirectangular mapping of a panorama (copyright (c) Didier Mouron under CC BY-SA license) :

Starting by the extraction of a rectilinear mapping of a specific part of the panorama shown by the following image :

we want to edit the color of the couch. Because distortions have been removed, the couch is much more easy to edit in a standard image editor. After editing, the rectilinear to equirectangular functions can be called to reproject back the rectilinear image into the panorama.

Moreover, the library allow to use a blending mask to perform specific correction. Changing the color of the couch in the following way :

the specific area that has to be edited in the panorama can be defined using a blending mask. Because objects distortion have been removed by the gnomonic projection, the mask can be build easely :

Using the blended rectilinear to equirectangular projection function, we can reproject the modification back into the original panorama :

The couch has now a much more ugly color. Those functions allow to work on panorama edition by removing the distortion due to equirectangular mapping. As a typical example, parallax phenomena can be specifically reduced using this technic.