[gdal-dev] 4 point, projective warping

[John Donovan]

I'd be very interested in a native GDAL implementation of perspective
warping. I've done something similar to the work Manuel has done on
Qgis, having written an in-house application that uses GSL/CBLAS. So I'd
be happy to help where I can, but as Manuel says, writing robust SVD
routines is beyond my ken.

So is another dependency the way to go?

-JD

-----Original Message-----
From: gdal-dev-bounces at lists.osgeo.org
[mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Jeffrey Warren
Sent: 01 August 2010 21:54
To: Manuel Massing
Cc: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] 4 point, projective warping

Thanks for all the input, Manuel - I've gone ahead with the ImageMagick
system and it works pretty well. That said, a projective warp would be
great as a native GDAL feature, so thanks for the offer.

If anyone else has interest, please pipe up! If it's just me then I
guess there's not too much demand.

Jeff

On 7/30/10, Manuel Massing <m.massing at warped-space.de> wrote:
> Hi Jeffrey,
>
>> I've thought about implementing a projective transform in the qgis 
>> georeferencer, so if you're interested I'll let you know when I get 
>> around to it.
>
> If this interest you, I have just commited an initial implementation 
> of projective warping (see 
> https://trac.osgeo.org/qgis/changeset/13987)
> to the qgis georeferencer, which is based on the gdalwarper.
>
> In principle, it should be relatively easy to integrate this transform

> into a custom version of gdalwarp.
>
> Maybe there's even interest to have such a transform in GDAL proper?
> I would be willing to contribute the code to GDAL, although the model 
> fitting step uses a singular value decomposition, so this would 
> require some dependency on  a linear algebra package (I wouldn't 
> consider it wise to reimplement numerical algorithms from scratch,
with their numerous caveats).
>
> cheers,
>
> 	Manuel
> 	
>
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