[gdal-dev] Can I change SOURCE_EXTRA setting at compile time?

[Frank Warmerdam]

Roger André wrote:
> Hi Frank,
> 
> I've theorized all sorts of reasons for what I'm seeing.  So far none of 
> them are right.  Basically, if I take a really high-res epsg:4326 image, 
> and serve it up through Mapserver in epsg:900913, there are instances 
> where I get images back which are missing rows of pixels at the bottom 
> of the image.  If I reduce the resolution of the image the lines go 
> away.  I haven't yet figured out at what resolution the problem starts 
> to appear.
> 
> I just tested the idea of changing the values in the warper code:
> First:
> nResWinSize += 100;
> Then:
> nResWinSize += 500;
> 
> Then rebuilt gdal.   Didn't seem to make a difference.

Roger,

Are you sure the GDAL warper is being used? If the reprojection is being
done by MapServer it will be using the MapServer warper.

Try changing the +- 1.0 values to larger values in the following code in
mapserver's mapresample.c:

/* -------------------------------------------------------------------- */
/*      Project desired extents out by 2 pixels, and then strip to      */
/*      available data.                                                 */
/* -------------------------------------------------------------------- */
     memcpy( &sOrigSrcExtent, &sSrcExtent, sizeof(sSrcExtent) );

     sSrcExtent.minx = floor(sSrcExtent.minx-1.0);
     sSrcExtent.maxx = ceil (sSrcExtent.maxx+1.0);
     sSrcExtent.miny = floor(sSrcExtent.miny-1.0);
     sSrcExtent.maxy = ceil (sSrcExtent.maxy+1.0);


See if that helps.  Currently there is no processing option that does
what SOURCE_EXTRA does, though it might be worth adding one.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent