def test_binary_header_size():
assert 400 == _segyio.binsize()
def test_read_and_write_trace(tmpdir):
binary = bytearray(_segyio.binsize())
_segyio.putfield(binary, 3213, 100)
_segyio.putfield(binary, 3221, 25)
f = get_instance_segyiofd(tmpdir, "trace-wrt.sgy", "w+", binary)
read_and_write_trace(f, False)
def create(filename, spec):
"""Create a new segy file.
Create a new segy file with the geometry and properties given by `spec`.
This enables creating SEGY files from your data. The created file supports
all segyio modes, but has an emphasis on writing. The spec must be
complete, otherwise an exception will be raised. A default, empty spec can
be created with ``segyio.spec()``.
Very little data is written to the file, so just calling create is not
sufficient to re-read the file with segyio. Rather, every trace header and
trace must be written to the file to be considered complete.
Create should be used together with python's ``with`` statement. This ensure
the data is written. Please refer to the examples.
The ``segyio.spec()`` function will default offsets and everything in the
mandatory group, except format and samples, and requires the caller to fill
in *all* the fields in either of the exclusive groups.
If any field is missing from the first exclusive group, and the tracecount
is set, the resulting file will be considered unstructured. If the
tracecount is set, and all fields of the first exclusive group are
specified, the file is considered structured and the tracecount is inferred
from the xlines/ilines/offsets. The offsets are defaulted to ``[1]`` by
``segyio.spec()``.
Parameters
----------
filename : str
Path to file to create
spec : segyio.spec
Structure of the segy file
Returns
-------
file : segyio.SegyFile
An open segyio file handle, similar to that returned by `segyio.open`
See also
--------
segyio.spec : template for the `spec` argument
Notes
-----
.. versionadded:: 1.1
.. versionchanged:: 1.4
Support for creating unstructured files
The ``spec`` is any object that has the following attributes
Mandatory::
iline : int or segyio.BinField
xline : int or segyio.BinField
samples : array of int
format : { 1, 5 }
1 = IBM float, 5 = IEEE float
Exclusive::
ilines : array_like of int
xlines : array_like of int
offsets : array_like of int
sorting : int or segyio.TraceSortingFormat
OR
tracecount : int
Optional::
ext_headers : int
Examples
--------
Create a file:
>>> spec = segyio.spec()
>>> spec.ilines = [1, 2, 3, 4]
>>> spec.xlines = [11, 12, 13]
>>> spec.samples = list(range(50))
>>> spec.sorting = 2
>>> spec.format = 1
>>> with segyio.create(path, spec) as f:
... ## fill the file with data
... pass
...
Copy a file, but shorten all traces by 50 samples:
>>> with segyio.open(srcpath) as src:
... spec = segyio.spec()
... spec.sorting = src.sorting
... spec.format = src.format
... spec.samples = src.samples[:len(src.samples) - 50]
... spec.ilines = src.ilines
... spec.xline = src.xlines
... with segyio.create(dstpath, spec) as dst:
... dst.text[0] = src.text[0]
... dst.bin = src.bin
... dst.header = src.header
... dst.trace = src.trace
Copy a file, but shorten all traces by 50 samples (since v1.4):
>>> with segyio.open(srcpath) as src:
... spec = segyio.tools.metadata(src)
... spec.samples = spec.samples[:len(spec.samples) - 50]
... with segyio.create(dstpath, spec) as dst:
... dst.text[0] = src.text[0]
... dst.bin = src.bin
... dst.header = src.header
... dst.trace = src.trace
"""
if not structured(spec):
tracecount = spec.tracecount
else:
tracecount = len(spec.ilines) * len(spec.xlines) * len(spec.offsets)
ext_headers = spec.ext_headers if hasattr(spec, 'ext_headers') else 0
samples = numpy.asarray(spec.samples, dtype = numpy.single)
binary = bytearray(_segyio.binsize())
_segyio.putfield(binary, 3217, 4000)
_segyio.putfield(binary, 3221, len(samples))
_segyio.putfield(binary, 3225, int(spec.format))
_segyio.putfield(binary, 3505, int(ext_headers))
f = segyio.SegyFile(str(filename), "w+", tracecount = tracecount,
binary = binary)
f._il = int(spec.iline)
f._xl = int(spec.xline)
f._samples = samples
if structured(spec):
f._sorting = spec.sorting
f._offsets = numpy.copy(numpy.asarray(spec.offsets, dtype = numpy.intc))
f._ilines = numpy.copy(numpy.asarray(spec.ilines, dtype=numpy.intc))
f._xlines = numpy.copy(numpy.asarray(spec.xlines, dtype=numpy.intc))
line_metrics = _segyio.line_metrics(f.sorting,
tracecount,
len(f.ilines),
len(f.xlines),
len(f.offsets))
f._iline_length = line_metrics['iline_length']
f._iline_stride = line_metrics['iline_stride']
f._xline_length = line_metrics['xline_length']
f._xline_stride = line_metrics['xline_stride']
f.text[0] = default_text_header(f._il, f._xl, segyio.TraceField.offset)
f.xfd.putbin(binary)
return f
def test_binary_header_size(self):
self.assertEqual(400, _segyio.binsize())