Copying color styling to color column in layer attribute table

Question

I have a polygon layer in QGIS that I have applied a random color style to each polygon. Under Layer Properties -> Style I selected a Categorized style and then generated a random color ramp. I added a color column to the layer table.

Is there a way to automatically copy the color assigned in the style to the color column for each polygon in the form "#ff0000"?

Ultimately, I want to export it as a GeoJSON layer and import it into a leaflet map. The color column will set the color in leaflet.

Answer 1

You could use PyQGIS for that (not sure is the best solution for it, though).

Assuming your layer has a color field (type: string), select (or activate) the layer in the QGIS ToC, open the QGIS Python console, and copy this code snippet:

layer = iface.activeLayer()
attr = layer.renderer().classAttribute()
attrColor = 'color'  # Name of the field to store colors
fieldIndex = layer.dataProvider().fieldNameIndex(attrColor)
attrFeatMap = {}

for cat in layer.renderer().categories(): 
    expr = "\"" + attr + "\"='" + unicode(cat.value()) + "'"

    for f in layer.getFeatures(expr):
        attrMap = {fieldIndex : cat.symbol().color().name()}
        attrFeatMap[f.id()] = attrMap
  
layer.dataProvider().changeAttributeValues( attrFeatMap )

After running it, you'll obtain this:

Let me know if you face any problem.