[Qgis-developer] Georeferencing using PyQGIS

[John Layt]

On 11 October 2015 at 21:03, Chris Schaffer <schaffecj at gmail.com> wrote:
> Hello,
>
> I would like to georeference a raster using PyQGIS.  If I want to
> georeference a raster manually (loaded from an ascii file), I can use the
> Georeferencer plugin, but I don't see a way to access this core C++ plugin
> using PyQGIS.
>
> When I tried using GDAL to georeference a raster, using the script created
> by selecting "Generate GDAL Script" in the Georeferencer, the raster was
> incorrectly georeferenced when I loaded it in QGIS. It looks like there may
> be differences between how GDAL and QGIS handle the georeferencing offsets.
>
> Do you have any advice for georeferencing a raster using PyQGIS, using the
> Georeferencer or otherwise?  I'm using QGIS 2.4.
>
> Thanks!
>
> Chris

You can't access the georeferencer from pyQGIS as it is a plugin
itself. You can find the plugin code at [1]. I would like to see it
all tidied up and exposed as public api, especially seeing as the
Helmert 2-point transform is not available in GDAL but is only
implemented in QGIS itself.

I did write my own georeferencer for our specialised purposes [2]
seeing as the QGIS gui is rather poor (45 clicks to 3-point georef
versus 5 in mine). There are Python bindings to gdal that you could
use instead [3], but I found it just easier to call the binaries
directly.

John.

[1] https://github.com/qgis/QGIS/tree/master/src/plugins/georeferencer
[2] https://github.com/jlayt/ArkPlan/tree/master/georef
[3] https://pypi.python.org/pypi/GDAL/