[gdal-dev] Georeference without rotation of output image

[Ivan Castellucci Vidal]

Hi, list

First of all, I searched on the list but I hadn't found anyone with the
same issue as me.

I'm working with aerial images of fields that I use as input to my program
which needs to process the images and find some visual patterns and then
give some output for the users.

I use georeferenced images because I need to extract geographic data after
my program process the image. So, when I warp my image with gdalwarp it
rotates the image and as a consequence of northing up the image, it rotates
the raster and adds 4 black triangles to make it rectangular.

The problem is, when I run my program, this "borders" are messing with my
algorithm and are a source of inaccuracy on the image processing. I can get
rid of them with more image processing but any extra step is
computationally heavy, specially when using large images.

I would need to avoid the rotation of the raster after gdalwarp is used to
implant the geotransformation on the destination image. I don't really care
if the image is not north up after warping it so I may not need gdalwarp
and instead I may be able to use some other solution based on the C API if
needed.

If it's relevant, the source images are in JPEG format and the destination
are in GeoTiff format, the transformation is done by using 3 (sometimes
more) GCPs and I'm using EPSG:4326 projection.

I didn't explained details of the pattern recognition process because I
think it's irrelevant to my problem and it will be confusing but if you
need any, just let me know.


Any help is appreciated,

Thanks in advance
-- 
Iván Castellucci Vidal
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