[gdal-dev] gdalwarp coordinate alignment with -tap option

[Even Rouault]

Le jeudi 13 février 2014 17:03:11, Gregory, Matthew a écrit :
> Hi Eli,
> 
> Eli Adam wrote:
> > <matt.gregory at oregonstate.edu> wrote:
> > > Hi all,
> > > 
> > > We have been using -tap as a command-line argument to gdalwarp to
> > > force pixels to be aligned with the origin (0,0) in the output
> > 
> > coordinate system.
> > 
> > > We now have a situation where we want to specify a different 'snap'
> > > coordinate for pixel alignment (e.g. (15,15)).  Is there a simple
> > > mechanism for specifying this within gdalwarp that I'm overlooking?
> > 
> > Not exactly sure what you mean.  But you might try using -tr as well.
> > I'm not exactly sure of how -tr and -tap relate from the docs,
> > 
> > -tr xres yres:set output file resolution (in target georeferenced units)
> > -tap:(GDAL >= 1.8.0) (target aligned pixels) align the coordinates of
> > the extent of the output file to the values of the -tr, such that the
> > aligned extent includes the minimum extent.
> 
> Thanks for your help.  I left out some key information from my initial post
> which was that I am also passing -tr 30 30 as an argument to gdalwarp. 
> When using -tap along with this, the pixels are aligned with the origin. 
> What I really want is for the 30m pixels to have a corner at (15, 15) in
> the output projection.
> 
> The only way I've figured out how to do this is to first find the projected
> extents of the output image (via osr in python), modify these extents to
> snap to my desired snap window and then use the -te command line option to
> explicitly set the extent.
> 
> I was just looking for an obvious way to specify this just using gdalwarp
> command line options.

Your method is the best method I can think of currently.

> 
> thanks, matt
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