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Support for regular and extended textual headers.

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This commit is contained in:
Robert Smallshire
2014-10-23 11:41:22 +02:00
parent ceb0f9bd61
commit 905ec4fe39
1 changed files with 91 additions and 48 deletions
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reader.py
+91 -48
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@@ -5,16 +5,16 @@ from util import file_length, filename_from_handle
from datatypes import DATA_SAMPLE_FORMAT, CTYPE_DESCRIPTION, CTYPES, size_in_bytes
from toolkit import (extract_revision,
bytes_per_sample,
read_reel_header,
read_binary_reel_header,
read_trace_header,
catalog_traces,
read_binary_values,
compile_trace_header_format,
REEL_HEADER_NUM_BYTES,
TRACE_HEADER_NUM_BYTES)
TRACE_HEADER_NUM_BYTES, read_textual_reel_header, read_extended_textual_headers)
def create_reader(fh, endian='>', progress=None):
def create_reader(fh, encoding=None, endian='>', progress=None):
"""Create a SegYReader (or one of its subclasses) based on performing
a scan of SEG Y data.
@@ -30,6 +30,10 @@ def create_reader(fh, endian='>', progress=None):
byte to be read. For disk-based SEG Y files, this is the
beginning of the file.
encoding: An optional text encoding for the textual headers. If
None (the default) a heuristic will be used to guess the
header encoding.
endian: '>' for big-endian data (the standard and default), '<'
for little-endian (non-standard)
@@ -81,21 +85,24 @@ def create_reader(fh, endian='>', progress=None):
if endian not in ('<', '>'):
raise ValueError("Unrecognised endian value {!r}".format(endian))
reel_header = read_reel_header(fh, endian)
revision = extract_revision(reel_header)
bps = bytes_per_sample(reel_header, revision)
textual_reel_header = read_textual_reel_header(fh, encoding)
binary_reel_header = read_binary_reel_header(fh, endian)
extended_textual_header = read_extended_textual_headers(fh, binary_reel_header, encoding)
revision = extract_revision(binary_reel_header)
bps = bytes_per_sample(binary_reel_header, revision)
trace_offset_catalog, trace_length_catalog, cdp_catalog, line_catalog = catalog_traces(fh, bps, endian, progress)
if cdp_catalog is not None and line_catalog is None:
return SegYReader2D(fh, reel_header, trace_offset_catalog, trace_length_catalog,
cdp_catalog, endian)
return SegYReader2D(fh, textual_reel_header, binary_reel_header, extended_textual_header, trace_offset_catalog,
trace_length_catalog, cdp_catalog)
if cdp_catalog is None and line_catalog is not None:
return SegYReader3D(fh, reel_header, trace_offset_catalog, trace_length_catalog,
line_catalog, endian)
return SegYReader3D(fh, textual_reel_header, binary_reel_header, extended_textual_header, trace_offset_catalog,
trace_length_catalog, line_catalog)
return SegYReader(fh, reel_header, trace_offset_catalog, endian)
return SegYReader(fh, textual_reel_header, binary_reel_header, extended_textual_header, trace_offset_catalog,
endian)
class SegYReader(object):
@@ -106,10 +113,17 @@ class SegYReader(object):
values. Traces can be accessed only by trace index.
"""
def __init__(self, fh, reel_header, trace_offset_catalog, trace_length_catalog, endian='>'):
def __init__(self,
fh,
textual_reel_header,
binary_reel_header,
extended_textual_header,
trace_offset_catalog,
trace_length_catalog,
endian='>'):
"""Initialize a SegYReader around a file-like-object.
Note:
Note:
Usually a SegYReader is most easily constructed using the
create_reader() function.
@@ -117,7 +131,12 @@ class SegYReader(object):
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
textual_reel_header: A sequence of forty 80-character Unicode strings
containing header data.
binary_reel_header: A dictionary containing reel header data.
extended_textual_header: A Unicode string (which may be empty).
trace_catalog: A mapping from zero-based trace index to
the byte-offset to individual traces within the file.
@@ -133,13 +152,15 @@ class SegYReader(object):
self._endian = endian
self._trace_header_format = compile_trace_header_format(self._endian)
self._reel_header = reel_header
self._textual_reel_header = textual_reel_header
self._binary_reel_header = binary_reel_header
self._extended_textual_header = extended_textual_header
self._trace_offset_catalog = trace_offset_catalog
self._trace_length_catalog = trace_length_catalog
self._revision = extract_revision(self._reel_header)
self._revision = extract_revision(self._binary_reel_header)
self._bytes_per_sample = bytes_per_sample(
self._reel_header, self.revision)
self._binary_reel_header, self.revision)
def trace_indexes(self):
"""An iterator over zero-based trace indexes.
@@ -190,7 +211,7 @@ class SegYReader(object):
raise ValueError("read_trace(): start value {} out of range 0 to {}"
.format(start, stop_sample))
dsf = self._reel_header['DataSampleFormat']
dsf = self._binary_reel_header['DataSampleFormat']
ctype = DATA_SAMPLE_FORMAT[dsf]
start_pos = (self._trace_offset_catalog[trace_index]
+ TRACE_HEADER_NUM_BYTES
@@ -235,13 +256,28 @@ class SegYReader(object):
return 1 if self.num_traces() == 1 else 0
@property
def reel_header(self):
"""The reel header, sometimes known as the binary header.
def textual_reel_header(self):
"""The textual real header.
Returns:
A dictionary containing data from the reel header.
An immutable sequence of forty Unicode strings each 80 characters long.
"""
return self._reel_header
return self._textual_reel_header
@property
def binary_reel_header(self):
"""The binary reel header.
A dictionary containing data from the reel header.
"""
return self._binary_reel_header
@property
def extended_textual_header(self):
"""The concatenation of any extended textual headers as a Unicode string.
If there were no headers, the string may be empty.
"""
return self._extended_textual_header
@property
def filename(self):
@@ -274,7 +310,7 @@ class SegYReader(object):
Returns:
One of the values from datatypes.DATA_SAMPLE_FORMAT
"""
return DATA_SAMPLE_FORMAT[self._reel_header['DataSampleFormat']]
return DATA_SAMPLE_FORMAT[self._binary_reel_header['DataSampleFormat']]
@property
def data_sample_format_description(self):
@@ -293,14 +329,16 @@ class SegYReader3D(SegYReader):
def __init__(self,
fh,
reel_header,
textual_reel_header,
binary_reel_header,
extended_textual_header,
trace_offset_catalog,
trace_length_catalog,
line_catalog,
endian='>'):
"""Initialize a SegYReader3D around a file-like-object.
Note:
Note:
Usually a SegYReader is most easily constructed using the
create_reader() function.
@@ -308,7 +346,7 @@ class SegYReader3D(SegYReader):
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
binary_reel_header: A dictionary containing reel header data.
trace_offset_catalog: A mapping from zero-based trace indexes to
the byte-offset to individual traces within the file.
@@ -322,8 +360,8 @@ class SegYReader3D(SegYReader):
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
"""
super(SegYReader3D, self).__init__(
fh, reel_header, trace_offset_catalog, trace_length_catalog, endian)
super(SegYReader3D, self).__init__(fh, textual_reel_header, binary_reel_header, extended_textual_header,
trace_offset_catalog, trace_length_catalog, endian)
self._line_catalog = line_catalog
def _dimensionality(self):
@@ -333,27 +371,27 @@ class SegYReader3D(SegYReader):
"""The number of distinct inlines in the survey
"""
try:
return self._line_catalog.j_max - self._line_catalog.j_min
return self._line_catalog.i_max - self._line_catalog.i_min + 1
except AttributeError:
# TODO: Memoize
return len(set(j for i, j in self._line_catalog))
return len(set(i for i, j in self._line_catalog))
def num_xlines(self):
"""The number of distinct crosslines in the survey
"""
try:
return self._line_catalog.i_max - self._line_catalog.i_min
return self._line_catalog.j_max - self._line_catalog.j_min + 1
except AttributeError:
# TODO: Memoize
return len(set(i for i, j in self._line_catalog))
return len(set(j for i, j in self._line_catalog))
def inline_xline_numbers(self):
"""An iterator over all (xline_number, inline_number) tuples
"""An iterator over all (inline_number, xline_number) tuples
corresponding to traces.
"""
return iter(self._line_catalog)
def trace_index(self, xline, inline):
def trace_index(self, inline, xline):
"""Obtain the trace index given an xline and a inline.
Note:
@@ -367,27 +405,28 @@ class SegYReader3D(SegYReader):
they may be).
Args:
xline: A crossline number.
inline: An inline number.
xline: A crossline number.
Returns:
A trace index which can be used with read_trace().
"""
return self._line_catalog[(xline, inline)]
return self._line_catalog[(inline, xline)]
class SegYReader2D(SegYReader):
def __init__(self,
fh,
reel_header,
textual_reel_header,
binary_reel_header,
extended_textual_header,
trace_offset_catalog,
trace_length_catalog,
cdp_catalog,
endian='>'):
cdp_catalog, endian='>'):
"""Initialize a SegYReader2D around a file-like-object.
Note:
Note:
Usually a SegYReader is most easily constructed using the
create_reader() function.
@@ -395,7 +434,7 @@ class SegYReader2D(SegYReader):
fh: A file-like object, which must support seeking and
support binary reading.
reel_header: A dictionary containing reel header data.
binary_reel_header: A dictionary containing reel header data.
trace_catalog_offset: A mapping from zero-based trace index to
the byte-offset to individual traces within the file.
@@ -408,8 +447,8 @@ class SegYReader2D(SegYReader):
endian: '>' for big-endian data (the standard and default), '<' for
little-endian (non-standard)
"""
super(SegYReader2D, self).__init__(
fh, reel_header, trace_offset_catalog, trace_length_catalog, endian)
super(SegYReader2D, self).__init__(fh, textual_reel_header, binary_reel_header, extended_textual_header,
trace_offset_catalog, trace_length_catalog, endian)
self._cdp_catalog = cdp_catalog
def _dimensionality(self):
@@ -490,10 +529,14 @@ def main(argv=None):
except AttributeError:
pass
#trace_index = segy_reader.trace_index(20, 300)
#trace_data = segy_reader.read_trace(trace_index, 200, 800)
pass
print("=== BEGIN TEXTUAL REEL HEADER ===")
for line in segy_reader.textual_reel_header:
print(line[3:])
print("=== END TEXTUAL REEL HEADER ===")
print()
print("=== BEGIN EXTENDED TEXTUAL HEADER ===")
print(segy_reader.extended_textual_header)
print("=== END EXTENDED TEXTUAL_HEADER ===")
if __name__ == '__main__':
main()