The number of bits per cell in the file, if it is not a power of 2 (i.e. 8, 16, or 32). Valid values are 1 - 32. If the bit depth is a power of 2, this value does not need to be specified. Note that previously the string "8-or-above" was equivalent to leaving this value blank.
When this value is specified, the interpretation of the input raster bands must be the minimum power of 2 above the requested bit depth. For example, to write 7-bit data, the interpretation must be one of UINT8, GRAY8, RED8, GREEN8, BLUE8, or ALPHA8.
When a value is specified, the writer will behave as follows:
- The writer checks the interpretation of the input raster bands. The interpretation of the input raster bands must be the minimum power of 2 above the requested bit depth. For example, to write 7-bit data, the interpretation must be one of UINT8, GRAY8, RED8, GREEN8, BLUE8, or ALPHA8.
- The data values on the bands will be reduced to the number of bits specified in the option. Note that values outside the bounds of the bit depth will be capped to the minimum or maximum. For example, if the number of bits is set to 4, a value of 201 (1100 1001 in base 2) will become 15 (1111 in base 2) in the output file.
- The NoData value on the bands will not change. For example, a NoData value 201 will still be 201 in the output file whatever the number of bits is set to. The user can change the NoData value before writing it to the format using the RasterBandNodataSetter transformer.
- The values of the palettes on the input raster will not change, but the number of palette entries does change. The maximum number of palette entries depends on the number of bits in the option. For instance, if the original palette has 256 entries with keys 0 to 255 and the number of bits is set to 4, keys 16 to 255 will be removed and the output palette will only have keys 0 to 15.