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

[Thomas Juntunen]

Jukka,

Have a look at Dan Stahlke's code he wrote when at GINA, I think
gdal_trace_ooutline will do what you want:
https://github.com/gina-alaska/dans-gdal-scripts

Thomas

On Tue, Oct 13, 2015 at 10:48 AM, Even Rouault <even.rouault at spatialys.com>
wrote:

> Le mardi 13 octobre 2015 13:19:50, Jukka Rahkonen a écrit :
> > 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.
>
> You can get the image to polygonize with :
> gdal_translate in.tif mask.tif -b mask
>
> That should work with images with nodata or alpha channel.
>
> > I guess that it would work but it feels a bit complicated. Is there any
> > more direct way for doing this task with GDAL?
>
> None that I can think of.
>
> gdal_polygonize.py would possibly do a bit more work than really needed in
> case there are holes of nodata inside the raster and you're not interested
> in
> such holes.
>
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-- 
*The right coordinate system can turn an impossible problem into two really
hard problems. -- Charlie Pellerin*

Thomas Juntunen
GIS Specialist
Polar Geospatial Center
R280 Learning and Environmental Science
1954 Buford Ave
University of Minnesota
St. Paul, MN 55108
612-626-0505
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