python3-segyio 1.5.2-1 / usr / lib / python3 / dist-packages / segyio / tools.py

import segyio
import numpy as np
import textwrap


def dt(f, fallback_dt=4000.0):
    """Since v1.1
    Find a *dt* value in the SegyFile. If none is found use the provided *fallback_dt* value.

    :type f: segyio.SegyFile
    :type fallback_dt: float
    :rtype: float
    """
    return f.xfd.getdt(fallback_dt)


def sample_indexes(segyfile, t0=0.0, dt_override=None):
    """Since v1.1

    Creates a list of values representing the samples in a trace at depth or time.
    The list starts at *t0* and is incremented with am*dt* for the number of samples.
    If a *dt_override* is not provided it will try to find a *dt* in the file.

    :type segyfile: segyio.SegyFile
    :type t0: float
    :type dt_override: float or None
    :rtype: list[float]
    """
    if dt_override is None:
        dt_override = dt(segyfile)

    return [t0 + t * dt_override for t in range(len(segyfile.samples))]


def create_text_header(lines):
    """
    Will create a "correct" SEG-Y textual header.
    Every line will be prefixed with C## and there are 40 lines.
    The input must be a dictionary with the line number[1-40] as a key.
    The value for each key should be up to 76 character long string.

    :type lines: dict[int, str]
    :rtype: str
    """
    rows = []
    for line_no in range(1, 41):
        line = ""
        if line_no in lines:
            line = lines[line_no]
        row = "C{0:>2} {1:76}".format(line_no, line)
        rows.append(row)

    rows = ''.join(rows)
    return rows

def wrap(s, width=80):
    """Since v1.1
    Formats the text input with newlines given the user specified width for each line

    :type s: str
    :type width: int
    :rtype: str
    """
    return '\n'.join(textwrap.wrap(str(s), width=width))


def native(data,
           format = segyio.SegySampleFormat.IBM_FLOAT_4_BYTE,
           copy = True):
    """ Convert numpy array to native float

    Since v1.1

    :type data: numpy.ndarray
    :type format: int|segyio.SegySampleFormat
    :type copy: bool
    :rtype: numpy.ndarray

    Converts a numpy array from raw segy trace data to native floats. Works for numpy ndarrays.

    Examples:
        Convert mmap'd trace to native float:
        >>> d = np.memmap('file.sgy', offset = 3600, dtype = np.uintc)
        >>> samples = 1500
        >>> trace = segyio.tools.native(d[240:240+samples])
    """

    data = data.view( dtype = np.single )
    if copy:
        data = np.copy( data )

    format = int(segyio.SegySampleFormat(format))
    return segyio._segyio.native(data, format)

def collect(itr):
    """ Collect traces or lines into one ndarray

    Since v1.1

    Eagerly copy a series of traces, lines or depths into one numpy ndarray. If
    collecting traces or fast-direction over a post-stacked file, reshaping the
    resulting array is equivalent to calling `tools.cube`.

    Examples:

    collect-cube identity::
        >>> f = segyio.open('post-stack.sgy')
        >>> x = segyio.tools.collect(f.traces[:])
        >>> x = x.reshape((len(f.ilines), len(f.xlines), f.samples))
        >>> numpy.all(x == segyio.tools.cube(f))

    :type itr: iterable[numpy.ndarray]
    :rtype: numpy.ndarray
    """
    return np.stack([np.copy(x) for x in itr])

def cube(f):
    """ Read a full cube from a file

    Since v1.1

    Takes an open segy file (created with segyio.open) or a file name.

    If the file is a prestack file, the cube returned has the dimensions
    (fast,slow,offset,sample). If it is post-stack (i.e. only the one offset),
    the dimensions are normalised to (fast,slow,sample)

    :type f: SegyFile|str
    :rtype numpy.ndarray
    """

    if not isinstance(f, segyio.SegyFile):
        with segyio.open(f) as fl:
            return cube(fl)

    ilsort = f.sorting == segyio.TraceSortingFormat.INLINE_SORTING
    fast = f.ilines if ilsort else f.xlines
    slow = f.xlines if ilsort else f.ilines
    fast, slow, offs = len(fast), len(slow), len(f.offsets)
    smps = len(f.samples)
    dims = (fast, slow, smps) if offs == 1 else (fast, slow, offs, smps)
    return f.trace.raw[:].reshape(dims)

def rotation(f, line = 'fast'):
    """ Find rotation of the survey

    Since v1.2

    Find the clock-wise rotation and origin of `line` as (rot,cdp-x,cdp-y)

    The clock-wise rotation is defined as the angle in radians between line
    given by the first and last trace of the first line and the axis that gives
    increasing CDP-Y, in the direction that gives increasing CDP-X.

    By default, the first line is the 'fast' direction, which is inlines if the
    file is inline sorted, and crossline if it's crossline sorted. `line`
    should be any of 'fast', 'slow', 'iline', and 'xline'.

    :type f: SegyFile
    :type line: str
    :rtype (float, int, int)
    """

    if f.unstructured:
        raise ValueError("Rotation requires a structured file")

    lines = { 'fast': f.fast,
              'slow': f.slow,
              'iline': f.iline,
              'xline': f.xline,
            }

    if line not in lines:
        error = "Unknown line {}".format(line)
        solution = "Must be any of: {}".format(' '.join(lines.keys()))
        raise ValueError('{} {}'.format(error, solution))

    l = lines[line]
    origin = f.header[0][segyio.su.cdpx, segyio.su.cdpy]
    cdpx, cdpy = origin[segyio.su.cdpx], origin[segyio.su.cdpy]

    rot = f.xfd.rotation( l.len,
                          l.stride,
                          len(f.offsets),
                          np.asarray(l.lines, order = 'C', dtype = np.intc) )
    return rot, cdpx, cdpy

def metadata(f):
    """ Get survey structural properties and metadata

    Since v1.4

    Create a descriptor object that, when passed to `segyio.create()`, would
    create a new file with the same structure, dimensions and metadata as `f`.

    Takes an open segy file (created with segyio.open) or a file name.

    :type f: SegyFile|str
    :rtype segyio.spec
    """

    if not isinstance(f, segyio.SegyFile):
        with segyio.open(f) as fl:
            return metadata(fl)

    spec = segyio.spec()

    spec.iline = f._il
    spec.xline = f._xl
    spec.samples = f.samples
    spec.format = f.format

    spec.ilines = f.ilines
    spec.xlines = f.xlines
    spec.offsets = f.offsets
    spec.sorting = f.sorting

    spec.tracecount = f.tracecount

    spec.ext_headers = f.ext_headers

    return spec

def resample(f, rate = None, delay = None, micro = False,
                                           trace = True,
                                           binary = True):
    """ Resample a file

    Since v1.4

    Resample all data traces, and update the file handle to reflect the new
    sample rate. No actual samples (data traces) are modified, only the header
    fields and interpretation.

    By default, the rate and the delay are in millseconds - if you need higher
    resolution, passing micro=True interprets rate as microseconds (as it is
    represented in the file). Delay is always milliseconds.

    By default, both the global binary header and the trace headers are updated
    to reflect this. If preserving either the trace header interval field or
    the binary header interval field is important, pass trace=False and
    binary=False respectively, to not have that field updated. This only apply
    to sample rates - the recording delay is only found in trace headers and
    will be written unconditionally, if delay is not None.

    This function requires an open file handle and is DESTRUCTIVE. It will
    modify the file, and if an exception is raised then partial writes might
    have happened and the file might be corrupted.

    This function assumes all traces have uniform delays and frequencies.

    :type f: SegyFile
    :type rate: int
    :type delay: int
    :type micro: bool
    :type trace: bool
    :type binary: bool
    """

    if rate is not None:
        if not micro: rate *= 1000

        if binary: f.bin[segyio.su.hdt] = rate
        if trace: f.header = { segyio.su.dt: rate}

    if delay is not None:
        f.header = { segyio.su.delrt: delay }

    t0 = delay if delay is not None else f.samples[0]
    rate = rate / 1000 if rate is not None else f.samples[1] - f.samples[0]

    f._samples = (np.arange(len(f.samples), dtype = np.single) * rate) + t0

    return f