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. Thanks for the info though. Roger -- On Tue, Nov 18, 2008 at 5:07 PM, Frank Warmerdam <[EMAIL PROTECTED]>wrote: > Roger André wrote: > >> I've been mercilessly beating a dead horse on a couple of lists about some >> weird artifacts that I'm getting when doing reprojections in Mapserver from >> epsg:4326 to epsg:900913. It's recently come to my attention that something >> was discussed in an IRC chat that might be pertinent to this issue, and I >> was hoping I could test it. Specifically, it relates to SOURCE_EXTRA, and >> although the conversation at the time dealt with issues at the International >> dateline, I think it might also manifest itself in other edge cases (literal >> edges). ;). >> >> I would like to know if it is possible to set SOURCE_EXTRA to something >> other than 1 at compile time? I do not see it listed as an option in the >> configure documentation, but perhaps I could edit a file, or pass in the >> flag anyhow? >> > > Roger, > > I haven't followed your problems closely (I recall something about datum > shifts). The SOURCE_EXTRA only helps with the GDAL warper. If you wanted > you could modify the following code in gdal/alg/gdalwarpoperation.cpp > and recompile: > > /* -------------------------------------------------------------------- */ > /* Allow addition of extra sample pixels to source window to */ > /* avoid missing pixels due to sampling error. In fact, */ > /* fallback to adding a bit to the window if any points failed */ > /* to transform. */ > /* -------------------------------------------------------------------- */ > if( CSLFetchNameValue( psOptions->papszWarpOptions, > "SOURCE_EXTRA" ) != NULL ) > { > nResWinSize += atoi( > CSLFetchNameValue( psOptions->papszWarpOptions, "SOURCE_EXTRA" > )); > } > else if( nFailedCount > 0 ) > nResWinSize += 10; > > > Perhaps change the nResWinSize += 10 line to nResWinSize += 100 or > something > like that. > > Best regards, > -- > > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > [EMAIL PROTECTED] > light and sound - activate the windows | > http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam> > and watch the world go round - Rush | Geospatial Programmer for Rent > >
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