When scanning a background, it is quite common that it does not enter the scanner and we have to scan it in parts. Joining it becomes a bit of a tedious job. To solve this, build the program quinema-hugin-completiva , scan each part of the background, make sure it has a reference between the Two parts.
quinema-hugin-completiva bg-1.png bg-2.png bg-out
quinema-hugin-completiva bg-out.tif bg-3.png bg
After this, the three parts of the example are united in the file bg.tif