[Qgis-developer] Re: Qgis Raster Calculator

[Tim Sutton]

Hi

Note: Tom its better etiquette to write these kind of messages on the
dev mailing list rather than mailing us directly. I'm replying to this
via the developer mailing list and it would be great if you could
continue the discussion there.


On Sun, Dec 5, 2010 at 5:59 PM, Tom Holderness
<tom.holderness at newcastle.ac.uk> wrote:
> Dear Peter,
>
> I'm e-mailing regarding the recent addition of the Raster calculator to Qgis 1.6.0 (and I've copied in a few others who may be interested).
>
> I am a third year PhD student, with a bachelors in Geographic Information Science, using long time-series Earth observation data for urban climate analysis. As part of my project (and as nothing suitable was available at the time) I wrote a basic Python library "PyRaster" based on GDAL for scripting of raster analysis routines (based on Numpy matrices), over large datasets (1000's of scenes). Other people in the research group are now using this for their own analysis, and recently I wrote a GUI in the form of a Qgis plugin the "raster processing suite" to make the library functions more accessible to non-technical users. The plugin includes a raster calculator and a recently added Python interface so that users can develop more advanced models (image processing code is generated on-the-fly from the GUI and presented to the user). This was my first Qt project so there are still a few things to improve before relasing v1.0 (current: 0.9.3).
>
> To save duplication of effort I wonder if my plugin and the Qgis raster calculator could be brought together to develop an in-built Qgis raster calculator within advanced processing capabilities.
>

I downloaded and tested your plugin using the link you provided below.
On the face of it I can't see any functionality it has that isnt in
the QGIS core raster calculator (but I only took a brief look), with
the exception of your python code generator - which is indeed an
interesting concept.

The QGIS raster calculator is written in C++ and includes some
features for dealing with rasters with different cell sizes etc, and
it has been included in the newish qgis_analysis libarary with an eye
to creating python bindings for it over time. It also has some
features that yours misses I think like the ability to create boolean
products using syntax lie raster at 1 < 100.



> I'm a big supporter of open-source geo projects (both my plugin and library are released under a BSD style license). There are obviously some technical "gaps" between the two projects, not least the difference between Python and C++ (I'm was a originally a C programmer), however, I would love to contribute to Qgis if possible.

Marco did the work on contract to me for a project and programmed it
in C++ for best speed and to get around the numpy in-memory aproach of
previous raster calculator efforts. It would be great if you were
interested to work directly on that. There are many features I would
like to see in the calculator which it currently lacks. If you were
interested in extending QGIS Raster Calculator I would be happy to
discuss some of the features it misses. We always encourage those who
wish to collaborate so if you have ideas, patches etc. just discuss
them on the mailing list / submit patches via trac etc. - your inputs
will certainly be appreciated.


>
> The plugin is available within my repository:
> www.students.ncl.ac.uk/tom.holderness/pyraster/qgis_repo.xml
> More information can be found at:
> www.students.ncl.ac.uk/tom.holderness/pyraster
>

Nice to see you are doing cool things with QGIS!

Regards

Tim

>
> Kind Regards,
>
> Tom
>
> ----------------------------------------------------
> Tomas du Chemin Holderness
> Postgraduate Researcher
>
> School of Civil Engineering and Geosciences
> Newcastle University
>
> Direct line:  +44 (0)191 222 6544
> Web: www.students.ncl.ac.uk/tom.holderness
>



-- 
Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
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