[GIS] Getting centroids for multiple lines in QGIS

centroidsgeometry-conversionlinepoint-creationqgis

Is there a possibility to get the centroid of each line?

When using Vector > Analysis Tools > Mean Coordinates I always get a centroid of the whole lines. What I need is the centroid of each line without having to select individual lines.

Best Answer

In tool "Mean coordinate(s)" from the QGIS's Processing Toolbox (Ctrl+Alt+T) use Unique "ID" field.

Colour

Use the following expression in the Expression String Builder

CASE
    WHEN "Field1" = 2 THEN '#264653'
    WHEN "Field1" = 9 THEN '#2A9D8F'
    WHEN "Field1" = 16 THEN '#E9C46A'
    WHEN "Field1" = 18 THEN '#F4A261'
    ELSE '#E76F51'
END

Line centroid symbology

Firstly Add symbol layer and make an SVG-marker out of it. After trying the following expression in the Expression String Builder for Dynamic SVG parameters

CASE
    WHEN "Field2" = 1 THEN 'P://Test//qgis_test//socicon_amazon.svg'
    WHEN "Field2" = 3 THEN 'P://Test//qgis_test//socicon_apple.svg'
    WHEN "Field2" = 8 THEN 'P://Test//qgis_test//socicon_github.svg'
    WHEN "Field2" = 13 THEN 'P://Test//qgis_test//socicon_google+.svg'
    ELSE 'P://Test//qgis_test//socicon_mail.svg'
END

Note: Central point was used for Marker placement.

Currently changing(overriding) simultaneously the colour and style of the SVG-file can not be done.

An Attempt

With this approach, you can get control over your symbology, see the image below.

Unfortunately, in this case, it is not possible to adjust the colour that easily. I was hoping to apply the method as was mentioned in one of my previous solutions.