[gdal-dev] How to find image footprints instead of envelopes?

[Jukka Rahkonen]

Hi,

This question appears every now and then in the gis.stackexchange and I have
been wondering about it by myself as well: How to generate a footprint
polygon of the real image data area so that the possible nodata areas would
not be included?

I have been thinking that I could convert the original image into a new
image with alpha channel or a one-bit image with nodata=0 and yesdata=1 and
then polygonize the alpha band or the 1-bit image with gdal_polygonize.py. I
guess that it would work but it feels a bit complicated. Is there any more
direct way for doing this task with GDAL? I bet that at least someone has
written a python script for it because the need is so obvious.

-Jukka Rahkonen-