[GIS] Using QGIS Geometry Generator to get rectangle from point

Question

I would like to translate a point (from a point layer) to a rectangle polygon using the new Geometry Generator from QGIS 2.14.

I know the length and the height of the resulting rectangle. The point should be the centroid.

Answer 1

While you can't do maths inside the WKT representation - you can use geom_from_wkt to turn a text string with maths in it back into a geometry. Something like:

geom_from_wkt( 
'POLYGON(('|| 
(x( centroid( $geometry) ) + 0.5)||' '||(y( centroid( $geometry) ) + 0.5)||','||
(x( centroid( $geometry) ) + 0.5)||' '||(y( centroid( $geometry) ) - 0.5)||','||
(x( centroid( $geometry) ) - 0.5)||' '||(y( centroid( $geometry) ) - 0.5)||','||
(x( centroid( $geometry) ) - 0.5)||' '||(y( centroid( $geometry) ) + 0.5)||','||
(x( centroid( $geometry) ) + 0.5)||' '||(y( centroid( $geometry) ) + 0.5)||','||
'))')