[Gdal-dev] Using gdal_merge to set pixels to transparent where nodata exists

[John Preston]

I'm using gdal_merge.py to combine a number of images into one. In
some cases there will be empty spaces in the output image, which I
wish to have set as transparent. Is there a way to set the pixels of
the output image to transparent before the merging starts, I'm
thinking some sort of -co NAME=PARAM option.

John