The raster3_layout.png was created from raster3_layout.xcf by export from GIMP
then resized to 540x477 using:
  mogrify -resize 540x480 raster3_layout.png

See also raster3d_tile_cell_generator.sh.

The image is used on several places in programming and user
documentation. To find all usages use:
  find . -name "*raster3d_layout.png"