Zarr v.2 filters — zarr

Zarr v.2 filters are transformations of chunk data that were not specified by Zarr v.2 itself but by the Numcodecs package that zarr-python uses. When a Zarr v.2 store is opened, the filters become codecs in the Zarr v.3 codec pipeline of an array, with a name of numcodecs.<id>. Because Zarr v.2 stores are read-only in this package, filters only decode data.

This class is the ancestor of all filters. It also implements the lossy "quantize" and "bitround" filters: these reduce the precision of floating point data upon encoding but they leave the data type unchanged, so decoding is the identity.

The following filters are supported: "delta", "fixedscaleoffset", "quantize", "bitround", "astype", "categorize", "packbits", "shuffle", "crc32", "adler32" and "fletcher32". The "vlen-utf8" filter is supported through zarr_codec_vlenutf8.

Super classes

zarr_extension -> zarr_codec -> zarr_filter

Active bindings

encoded_type: (read-only) The zarr_data_type of the encoded data, or NULL if the filter does not change the data type. This is the data type that the "bytes" codec must deserialize.

Methods

Inherited methods

`zarr_filter$new()`

Create a new filter object.

Usage

zarr_filter$new(id, configuration, from = "array", to = "array")

Arguments

id: The Numcodecs identifier of the filter, such as "delta".
configuration: A list with the configuration parameters of the filter, as found in the Zarr v.2 metadata but without the "id" element.
from, to: The input and output data object for the encoding operation, either "array" or "bytes".

Returns

An instance of this class.

`zarr_filter$copy()`

Create a new, independent copy of this filter.

Usage

zarr_filter$copy()

Returns

An instance of the same class as this filter.

`zarr_filter$encode()`

Filters can only decode data: Zarr v.2 stores are read-only.

Usage

zarr_filter$encode(data)

Arguments

data: Ignored.

Returns

This method always throws an error.