Hello, some time ago I complained with this list, asking for a better algorithm for black and white and paletted raster maps. While you scale the image, smaller black lines become thinner and thinner, scaling to half size usually works without data loss but further size reductions result into severe data loss. I suggested introducting an "erose" option as to make thin lines become fatter while reducing size.
Evaluating the consequences of the proposal, Even Rouault suggested this was not a task for GDAL, but a user level choice to be provided by QGis or other programs. This is true, well known and expensive proprietary map-something show antialised raster layers without any special effort, but at the expense of huge computational requests. Now, making pyramids should substantially reduce this burden, but without severe data loss. Obviously, Even is right, client programs should design a better strategy to deal with line art and paletted maps, they could take into account a near scale pyramid and an higher resolution one to draw antialised layers in a slower rendition (this approach could be user selectable or automatical, based on raster type), but it's still true that GDAL should do its part not to lose data. And that happens without any choice by the user than to avoid pyramids. Could we do something better? _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
