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

[Frank Warmerdam]

John Preston wrote:
> 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,

This does not currently exist, and *could* be added.  But I'm hesitant
to wedge too many more features into gdal_merge.py which I'm trying to
superceed with gdalwarp.

But if you feel the need, it should be relatively easy to add a pass
over the file, setting it to some initial nodata value after it's
creation.

Best regards,
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