Related to question: Removing black background and black font from raster in QGIS
I have also a black backround and when doing as it is suggested in the answer the black backround goes away but also points from the image within the region I want to keep are also erased. There may be black dots which dissapear when doing this. So white dots appear. I thought the option "clip the extent of the target dataset to the extent of the cutline" should control from which line on the nodata should be applied but it isn´t the case. I have tried all the options (0, 100, leaving it empty, ...). Is there another thing I could do?