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I have a tiff image file and want to get a polygon with the extent of the tiff. Is there a direct way of doing this? Right now i have to convert the image to vector (with gdal_polygonize) and then dissolve the polygons...

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I'm not versed with the QGIS API, but would this help? – dassouki Nov 14 '11 at 18:30
yes, QgsRectangle sounds like what i want, but how do I use it?... – vascobnunes Nov 14 '11 at 18:34
I think this is a better example from the pyqgis cookbook. If you get the extents, you can use this to create the vector bound – dassouki Nov 14 '11 at 18:48
up vote 4 down vote accepted

Your question isn't clear. Do you want the 'rectangular' extents of the raster, or the extent of the features in the raster? For the rectangular extent, just use the "Tile Index" under Raster > Miscellanious > Tile Index. If you don't see the Raster menu, you may have to install or enable the GDALTools plugin.

And of course if you aren't tied to doing it in QGIS, you could just use GDAL directly. See gdaltileindex

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is there a way to create a polygon from the extent of the features in the raster? Not the 'rectangular' extents. – Bluefox Mar 23 at 5:43
You could try converting the raster to vector, then using a 'concave hull' or 'alpha shape' to create the 'extents' although it seems like a lot of work. What is your ultimate goal? Perhaps there's an easier way... – Darren Cope Mar 23 at 20:37
would you be able to answer my question… Well the ultimate goal will be to crop a dem to the extents within the features, after which run a topographic correction of a landsat image. – Bluefox Apr 2 at 18:40

If you want only the extent of one image and not the full directory you can go to Vector->Research Tool->Polygon from layer extent here select the image you want the extent and save the output.

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