orangecontrib: doc: add minimal documentation for I normalization

doc/index.rst

@@ -126,6 +126,7 @@ Reconstruction
   widgets/reconstruction/sadeltabetawidget.rst
   widgets/reconstruction/tofuwidget.rst
   widgets/reconstruction/castvolumewidget.rst
+  widgets/reconstruction/intensitynormalization.rst
 
 
 Cluster

doc/widgets/reconstruction/intensitynormalization.rst

+.. _intensity normalization:
+
+I normalization
+```````````````
+
+.. image:: img/intensity_normalization/main_screen.png
+
+
+Behavior
+''''''''
+
+The goal of this widget is to let the user define some normalization to be applied to sinograms.
+This normalization can be one of the following:
+
+* None: no extra normalization will be applied to the sinogram
+* chebyshev: chebyshev normalization will be applied to sinograms
+* division: a value or an array of value will divide the sinogram (during nabu preprocessing step)
+* subtraction: a value or an array of value will subtract the sinogram (during nabu preprocessing step)
+
+For **division** and **subtraction** the user can either provide:
+
+* a scalar value which will be constant
+* a roi to compute one scalar value *per projections* in order to be applied on the sinogram.
+* an URL to be provided directly to nabu. In this case the dataset can be provided locally or globally.
+  If provided locally then the path will be updated for each scan. If provided globally then it will be constant.