FixedScaleOffset#

class numcodecs.fixedscaleoffset.FixedScaleOffset(offset, scale, dtype, astype=None)[source]#

Simplified version of the scale-offset filter available in HDF5. Applies the transformation (x - offset) * scale to all chunks. Results are rounded to the nearest integer but are not packed according to the minimum number of bits.

Parameters:

offsetfloat: Value to subtract from data.
scalefloat: Value to multiply by data.
dtypedtype: Data type to use for decoded data.
astypedtype, optional: Data type to use for encoded data.

See also

numcodecs.quantize.Quantize

Notes

If astype is an integer data type, please ensure that it is sufficiently large to store encoded values. No checks are made and data may become corrupted due to integer overflow if astype is too small.

Examples

>>> import numcodecs
>>> import numpy as np
>>> x = np.linspace(1000, 1001, 10, dtype='f8')
>>> x
array([1000.        , 1000.11111111, 1000.22222222, 1000.33333333,
       1000.44444444, 1000.55555556, 1000.66666667, 1000.77777778,
       1000.88888889, 1001.        ])
>>> codec = numcodecs.FixedScaleOffset(offset=1000, scale=10, dtype='f8', astype='u1')
>>> y1 = codec.encode(x)
>>> y1
array([ 0,  1,  2,  3,  4,  6,  7,  8,  9, 10], dtype=uint8)
>>> z1 = codec.decode(y1)
>>> z1
array([1000. , 1000.1, 1000.2, 1000.3, 1000.4, 1000.6, 1000.7,
       1000.8, 1000.9, 1001. ])
>>> codec = numcodecs.FixedScaleOffset(offset=1000, scale=10**2, dtype='f8', astype='u1')
>>> y2 = codec.encode(x)
>>> y2
array([ 0,  11,  22,  33,  44,  56,  67,  78,  89, 100], dtype=uint8)
>>> z2 = codec.decode(y2)
>>> z2
array([1000.  , 1000.11, 1000.22, 1000.33, 1000.44, 1000.56,
       1000.67, 1000.78, 1000.89, 1001.  ])
>>> codec = numcodecs.FixedScaleOffset(offset=1000, scale=10**3, dtype='f8', astype='u2')
>>> y3 = codec.encode(x)
>>> y3
array([ 0,  111,  222,  333,  444,  556,  667,  778,  889, 1000], dtype=uint16)
>>> z3 = codec.decode(y3)
>>> z3
array([1000.   , 1000.111, 1000.222, 1000.333, 1000.444, 1000.556,
       1000.667, 1000.778, 1000.889, 1001.   ])

codec_id: str | None = 'fixedscaleoffset'#: Codec identifier.

encode(buf)[source]#

Encode data in buf.

Parameters:

bufbuffer-like: Data to be encoded. May be any object supporting the new-style buffer protocol.

Returns:

encbuffer-like: Encoded data. May be any object supporting the new-style buffer protocol.

decode(buf, out=None)[source]#

Decode data in buf.

Parameters:

bufbuffer-like: Encoded data. May be any object supporting the new-style buffer protocol.
outbuffer-like, optional: Writeable buffer to store decoded data. N.B. if provided, this buffer must be exactly the right size to store the decoded data.

Returns:

decbuffer-like: Decoded data. May be any object supporting the new-style buffer protocol.

get_config()[source]#: Return a dictionary holding configuration parameters for this codec. Must include an ‘id’ field with the codec identifier. All values must be compatible with JSON encoding.

classmethod from_config(config)#: Instantiate codec from a configuration object.

FixedScaleOffset#

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