I have a NDVI image, which I Geo-referenced in QGIS (raster). Now I have to open the image in Google Earth - how do I convert the GeoTIFF raster file to a kml file in QGIS, so that I can open the image as a layer in Google Earth?
These days you can use Google Earth Pro for free:
Note: Google Earth Pro requires a license key. If you do not have a key, use your email address and the key GEPFREE to sign in.
Google Earth Pro should be able to load directly your GeoTIFF (and save as something else if you need).
To display the image is Google Earth, your CRS has to be EPSG:4326. So re-project your image first if required.
Then, you can use gdal2tiles.py script which will create a KML SuperOverlay and you can view it in Google Earth.