You could create a polygon in qgis (or some automated way), find an unused pixel value in the chart, and then use gdal_rasterize -i to burn it into the collar area. You can then use that as the transparency value.
On Wed, Mar 18, 2009 at 3:32 PM, Chris h <chris...@magma.ca> wrote: > On Wednesday 18 March 2009 16:07:18 MS wrote: > > I realize this goes into other software on a qgis list, but I wonder > > with GDAL or GRASS one can accomplish this. > > > > It is really a raster clip that would work well, especially if the > > next step is mosaic'ing the rasters. Are these quad ma > > The charts are NOAA BSB rasters. > > Posted the same questions to the grass list and the response was positive: > ------------------------------------------------ > >> WIth r.in.poly you could "digitize" the area of interest, then use > >> r.mask to remove the outside area, then r.patch everything. > >> With a small script you could generate the ASCII polygon file > >> for r.in.poly based on the map extent. > -------------------------------------------------- > > Standalone gdal will not do it, especially if you want to automate the > process > and have concerns with the osmerander bug which in a marine charting > environment could be rather interesting. The charts will in fact be tiled > and > made available via mapserver wms. > > The only issue for me is that I must learn each step with each application. > Hence I went the easy route first to see what can be done with qgis. > > There is a very good new program out for creating tiles, maptiler.org and > need > to see and learn if the datum and projection can be changed. Its basically > a > front end to galtiler. > > Thanks for all the suggestions. > > > -- > /ch > _______________________________________________ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user >
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