Sunday 25 June 2017

qgis - How to add my own GRASS algorithms to Processing?



I need to use algorithm r.bioclimatic from GRASS in QGIS but I see that this algorithm don't exist in Processing Toolbox. A search a way of add this algorithm to Processing and in GRASS and Sextante page if find this way:


HOWTO adding own GRASS algorithms to Sextante (simply by adding a new description file)


I create a description file according to the rules but now I don't know how to run and if this will run in GRASS.


The first parameters of r.bioclimatic (tmin, tmax....) are columns of tables? I don't know which type of input I have.



Answer



r.bioclim (I suppose, because r.bioclimatic don't exist), is an GRASS GIS 7 addon


If you want to create or modify an algorithm, read the file ../processing/algs/grass7/grass7.txt that begins with "A short guide for creating and editing GRASS GIS 7 algorithms"


But, how do these commands work ?



  • to use the GRASS7 commands in processing,you need to first specify the GRASS GIS installation (in Processing/options) and processing will look for scripts that are in the folders bin and scripts of your GRASS installation (GISBASE environment variable) in the script ../processing/algs/grass7/Grass7AlgorithmProvider.py


  • the script is executed with the Python module subprocess in the ../processing/algs/grass7/Grass7Utils.py script


The big problem is that the addons are not installed in these folders (GRASS_ADDON_PATH environment variable) therefore you can simply use them with processing


Conclusion ? QGIS is not GRASS GIS and if you want to use a "specialized" algorithm (addon), use GRASS GIS


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