How to add Geospatial Coordinates to PNG images?

How to add Geospatial Coordinates to PNG images?

With PDF3D ReportGen  Geospatial Coordinates can be applied to PNG file in three ways:
a) create a .pgw world file with the same name as your PNG,
b) create a .proj projection file containing well-known-text (WKT) coordinates, such as EPSG code,
c) assign it manually using the Geospatial tab menus in ReportGen, but this is mostly about the 3D model, so if draping onto a surface the image should come in already georeferenced.
Also try GeoTIFF format, which can carry the coordinates within the file.