Select Features by polygon colour

Question

I am using QGIS V3.22.6.

I have imported a set of polygons digitised in Google Earth. They all have the same name but have different polygon colours.

I would like to rename these according to their colour, but am unable to work out how to select the polygon by colour.

Answer 1

You need a script to select same colored features because the kml layer uses "Embedded Symbols" and the attribute table doesn't include any information about colors or polygons with same color.

• Open Python Editor (Ctrl+Alt+P then click middle icon)
• Select the layer and run this script.

# get active layer
layer = iface.activeLayer()
# feature list
features = list(layer.getFeatures(QgsFeatureRequest().setFlags(QgsFeatureRequest.EmbeddedSymbols)))
# embedded symbols
symbols = [f.embeddedSymbol().clone() if f.embeddedSymbol() else None for f in features]
# colors of embedded symbols
colors = {f.id(): s.color().name() for f, s in zip(features, symbols)}

for color in set(colors.values()):
    # features with the same color
    feature_ids = [fid for fid, c in colors.items() if c == color]
    layer.selectByIds(feature_ids) # select the features
    
    # extract the selected features as temporary layer
    output = processing.run("native:saveselectedfeatures",
                            {'INPUT':layer,
                             'OUTPUT':'TEMPORARY_OUTPUT'})["OUTPUT"]
                             
                             # set color and name for the output
    output.renderer().symbol().setColor(QColor(color))
    output.setName(color)
    
    # add the layer to the project
    QgsProject.instance().addMapLayer(output)