[gdal-dev] Boundary Artifact with ChunkAndWarpImage

[Even Rouault]

Le jeudi 16 avril 2015 19:01:57, Michael Aschenbeck a écrit :
> Hello,
> 
> I'm using ChunkAndWarpMulti to warp an image.  The warping is working
> nicely, however, at the boundary I seem to be getting some artifacts.
> 
> The first artifact i see is a DARK boundary of pixels in some location.  My
> guess is that the interpolator is interpolating with blackfill (intensity
> zero pixels).  Note that I am using the following setup:
> psWarpOptions->padfSrcNoDataReal = (double *)
> CPLMalloc(psWarpOptions->nBandCount*sizeof(double));
> for (int ii = 0; ii < psWarpOptions->nBandCount; ii++)
> {
> psWarpOptions->padfSrcNoDataReal[ii] = 0;
> }
> which i thought was supposed to treat zeros as nodata.  It doesn't seem to
> be doing what I think it should.
> 
> In some cases, I am also noticing a BRIGHT band strip of pixels adjacent to
> the dark boundary pixels.  I don't have any thoughts on where this artifact
> is coming from.
> 
> Below you can find links to an example.  The orange you see is just the
> background color of my viewer.  Zero pixels are set to transparent so you
> can see the dark boundary artifact.  (Note that all of the orange region is
> covered with zero-intensity pixels, so we haven't reached the boundary of
> the file, just the boundary of the non-zero pixels.)  Sorry if that's
> confusing.
> The before image: https://www.dropbox.com/s/3kmyi8wu0qybsq9/before.JPG?dl=0
> The after image with the artifacts:
> https://www.dropbox.com/s/fo0m8q95b26s61m/after.JPG?dl=0
> 

Mike,

Which gdal version ? Which resampling method ?
Do you reproduce with gdalwarp ?
If so, providing input file + full gdalwarp command line would help.

Even

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