I have a raster with buildings that look darker. I want to detect the dark areas and enclose them with a polygon

enter image description here

this is what i want to achieve, or something similar. enter image description here

What tools could I use with QGIS, ArcGIS, or Python to achieve this?

  • First you have to choose a platform and make an attempt. Since there's already a QGIS Answer, you should probably choose QGIS for this Question.
    – Vince
    Commented Sep 26, 2022 at 23:57

1 Answer 1


This amounts to translating the values ​​contained in the pixels to obtain a layer vectorized thematic information. It is a work of classification. There are several methods. You can do it with QGIS (for example after having installed for example the OTB toolbox libraries (to download here: enter link description here or the plug in QGIS, the Semi-Automatic Classification Plugin (SCP) (to download here : `enter link description here

There are tutorials : enter link description here

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