I have been trying to convert the background of several images to
transparent, but what I was able to do with gdaldem is to convert all the
image to transparent and with gdalwarp although it converts the background
to transparent, the other colors are set to green.
Don't really know what to do to have the desired output.
So what I would like, is to keep the colors that are not part of the
background. I am not able to select only the color that I want from the
image and set only that color to transparent.
Any advice is much appreciated.