This question already has an answer here:
That question addresses why the TIF imported into QGIS has a dark gray background when the color set is set to 4096 when exported from PDFCreator. That file's gdalinfo shows NBITS=4
Here, in this question, I would like to know if there is a way to render the dark gray transparent, much in the way that entering a "0" in properties->transparency->no data value->additional no data value will make the black lines transparent.
Alternatively, is there a way to have QGIS render the dark gray as white?