I am trying to vectorize a raster whose digital numbers indicate different classes they belong to. ArcGIS and QGIS yield similar results: separate shapes out of pixels sharing the class that are adjacent only diagonally. In this sense, this question is related with this one and also this one.
I tried the suggestions posted in those questions, but none of them worked for me. I can not use the buffering-approach because my polygons refer to networks of areas; the connectivity/topology of those networks must remain intact, and I have nodes very close to each other. Dissolve is not useful either; it apparently does not work on polygons sharing a single vertex.
ILWIS could solve the issue:
I found that the vectorization tool of ILWIS (see explanation here) has an option for scanning for the 8 neighboring pixels during the targeting of each raster pixel to a polygon. ILWIS calls it "Output map 8-connected with smoothing". This might solve the issue by avoiding the polygon breakage during the vectorization when input pixels are placed diagonally.
I downloaded and installed the ILWIS version available here. However, after importing the raster I want to vectorize (I used the built-in GDAL option), the drop-down menu to select the input layer in the 'Raster to Polygon' tool does not allow me to select anything and thus I can not use the tool.
Does somebody know how to use this ILWIS' tool, or how to solve this problem?