mapnik-org/mapnik — Issue #561: GDAL pre-scaling, overviews, and bilinear scaling don't play nicely
Author: artemp
Created: 2011-10-11 08:01:56+00:00
State: open
Labels: GDAL_Input_Driver

If bilinear scaling is used in a style applied to a raster layer, we need to make sure that the data queried from the datasource and passed to the agg_renderer is at least 1.5 to 2 times larger than the target map size. This is needed both for the raster plugin and the gdal plugin, but is more critical for the gdal plugin because pre-scaled data from overviews from gdal can result in lower quality.

Will require changes to the mapnik::query object to be able to pass scaling directives to the layer/datasource from feature_style_processor.cpp. It may be useful to globally set/overridden the down sampling factor (how much larger of a size to query for later downsampling) at the layer level to allow for debugging (maybe in the future moving to a RasterSymbolizer style property if performance is not hindered).