raster_tools.read_color_table#

raster_tools.read_color_table(path, band=1)[source]#

Read the color table attached to a raster file.

The table is returned exactly as it is stored, which for a GeoTIFF means padded out to the full index range of the band’s dtype: 256 entries for uint8 and 65536 for uint16, with undefined entries set to opaque black. An eight class table therefore comes back with 256 entries.

The padding cannot be filtered out reliably. An undefined entry is (0, 0, 0, 255), which is indistinguishable from a deliberate black entry, and a black class is common in categorical data where it marks background. Trim the result against the values a raster actually uses if a compact table is needed.

Parameters

path (str, pathlib.Path) – The path to the raster file to read the color table from.
band (int, optional) – The 1-based band to read the table from. The default is the first band. A raster file can only carry a table on its first band.

Returns

Maps each raster value to an (r, g, b, a) tuple of ints in the range 0-255. The result can be handed straight back to Raster.save() as its color_table argument.

Return type

dict

Raises

raster_tools.exceptions.RasterIOError – Raised if the file cannot be opened, or if the requested band has no color table.
IndexError – Raised if band is not a band in the file.