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Add note about band=N being needed for RasterColorizer to work

Sandro Santilli 2014-07-04 02:21:32 -07:00
parent 8918d57729
commit 573a4878be
1 changed files with 1 additions and 1 deletions
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GDAL.md

@ -23,7 +23,7 @@ To check if the gdal plugin built and was installed correctly you can do:
|:------------|----------|---------------|----------:|
| file | string | file of the raster to be read | |
| base | string | base path where to search for file parameter | |
| band | integer | request for a specific raster band index, -1 means all bands | -1 |
| band | integer | request for a specific raster band index, -1 means all bands. Note that a band read from a single band raster gets interpreted as Grayscale if band=-1 is specified while they retain their original value when explicitly referenced with the "band" parameter. This affects effectiveness of [[RasterColorizer]] | -1 |
| nodata | double | allow setting nodata value on the fly (will override value if nodata is set in data) | |
| shared | boolean | Whether to open the dataset in shared mode. Not recommend to enable true unless you can guarantee that one on thread accesses a given file at the same time (unlikely given the way that most tiling software works with mapnik). It is only beneficial therefore if you are rendering multiprocess and single threaded and are working in low memory situation. Internally it directs Mapnik to call `GDALOpenShared` instead of `GDALOpen` which means that GDAL will consult its global cache of datasets. GDAL will try to return a copy of the dataset if access from multiple threads (but this defeats the purpose of sharing) | false |