I am getting a black
image when I try to display PostGIS out-db rasters. I discovered that it
has to do with GDAL support for out-db rasters as stated in the link
below for a similar issue (over 1 year back): https://hub.qgis.org/issues/12133
last comment by Jürgen Fischer states "... only black images. So it's a
dependency issue (GDAL complains ERROR 1: This raster has outdb
storage. This feature isn't still available)."