def write_segy_based_on(hf, segy_y_reader, data, endian='>'):
"""
Purpose:
make it easy to write new (processed) data back to a new segy file based on the original
segy file
Args:
fh: A file-like object open for binary write.
segy_y_reader: a SegYReader instance from which the segy headers and other parameters can be retreived
data: a numpy array containing trace samples organised in (trace, inline, crossline order)
"""
encoding = segy_y_reader.encoding
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, segy_y_reader.textual_reel_header, encoding)
write_binary_reel_header(fh, segy_y_reader.binary_reel_header, endian)
write_extended_textual_headers(fh, segy_y_reader.extended_textual_header, encoding)
trace_header_packer = HeaderPacker(trace_header_format, endian)
il_xl = list(itertools.product(segy_y_reader.inline_range(), segy_y_reader.xline_range()))
x_y = list(itertools.product(range(0,segy_y_reader.num_inlines()), range(0,segy_y_reader.num_xlines())))
for ix,ij in zip(il_xl, x_y):
idx = reader.trace_index((ix[0],ix[1]))
write_trace_header(fh, segy_y_reader.trace_header(idx), trace_header_packer)
write_trace_samples(fh, data[:,ij[0],ij[1]], segy_y_reader.data_sample_format, endian=endian)
def write_segy(fh,
dataset,
encoding=None,
trace_header_format=TraceHeaderRev1,
endian='>',
progress=None):
"""
Args:
fh: A file-like object open for binary write, positioned to write the textual reel header.
dataset: An object implementing the interface of segpy.dataset.Dataset, such as a SegYReader.
trace_header_format: The class which defines the layout of the trace header. Defaults to TraceHeaderRev1.
encoding: Optional encoding for text data. Typically 'cp037' for EBCDIC or 'ascii' for ASCII. If omitted, the
seg_y_data object will be queries for an encoding property.
endian: Big endian by default. If omitted, the seg_y_data object will be queried for an encoding property.
progress: A unary callable which will be passed a number
between zero and one indicating the progress made. If
provided, this callback will be invoked at least once with
an argument equal to one.
Raises:
UnsupportedEncodingError: If the specified encoding is neither ASCII nor EBCDIC
UnicodeError: If textual data provided cannot be encoded into the required encoding.
"""
progress_callback = progress if progress is not None else lambda p: None
if not callable(progress_callback):
raise TypeError("write_segy(): progress callback must be callable")
encoding = encoding or (hasattr(dataset, 'encoding')
and dataset.encoding) or ASCII
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, dataset.textual_reel_header, encoding)
write_binary_reel_header(fh, dataset.binary_reel_header, endian)
write_extended_textual_headers(fh, dataset.extended_textual_header,
encoding)
trace_header_packer = make_header_packer(trace_header_format, endian)
num_traces = dataset.num_traces()
for trace_index in dataset.trace_indexes():
write_trace_header(fh, dataset.trace_header(trace_index),
trace_header_packer)
write_trace_samples(fh,
dataset.trace_samples(trace_index),
dataset.data_sample_format,
endian=endian)
progress_callback(trace_index / num_traces)
progress_callback(1)
def write_segy(fh,
seg_y_data,
encoding=None,
trace_header_format=TraceHeaderRev1,
endian='>',
progress=None):
"""
Args:
fh: A file-like object open for binary write, positioned to write the textual reel header.
seg_y_data: An object from which the headers and trace_samples data can be retrieved. Requires the following
properties and methods:
seg_y_data.textual_reel_header
seg_y_data.binary_reel_header
seg_y_data.extended_textual_header
seg_y_data.trace_indexes
seg_y_data.trace_header(trace_index)
seg_y_data.trace_samples(trace_index)
seg_y_data.encoding
seg_y_data.endian
One such legitimate object would be a SegYReader instance.
trace_header_format: The class which defines the layout of the trace header. Defaults to TraceHeaderRev1.
encoding: Optional encoding for text data. Typically 'cp037' for EBCDIC or 'ascii' for ASCII. If omitted, the
seg_y_data object will be queries for an encoding property.
endian: Big endian by default. If omitted, the seg_y_data object will be queried for an encoding property.
progress: An optional progress bar object.
Raises:
UnsupportedEncodingError: If the specified encoding is neither ASCII nor EBCDIC
UnicodeError: If textual data provided cannot be encoded into the required encoding.
"""
encoding = encoding or (hasattr(seg_y_data, 'encoding')
and seg_y_data.encoding) or ASCII
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, seg_y_data.textual_reel_header, encoding)
write_binary_reel_header(fh, seg_y_data.binary_reel_header, endian)
write_extended_textual_headers(fh, seg_y_data.extended_textual_header,
encoding)
trace_header_packer = make_header_packer(trace_header_format, endian)
for trace_index in seg_y_data.trace_indexes():
write_trace_header(fh, seg_y_data.trace_header(trace_index),
trace_header_packer)
write_trace_samples(fh,
seg_y_data.trace_samples(trace_index),
seg_y_data.data_sample_format,
endian=endian)
def write_extended_textual_headers(fh, pages, encoding):
"""Write extended textual headers.
Args:
fh: A file-like object open in binary mode for writing.
pages: An iterables series of sequences of Unicode strings, where the outer iterable
represents 3200 byte pages, each comprised of a sequence of exactly 40 strings of nominally 80 characters
each. Although Unicode strings are accepted, and when encoded they should result in exact 80 bytes
sequences. To produce a valid data structure for pages, consider using format_extended_textual_header()
encoding: Either 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be position at the first byte after the extended textual headers, which is
also the first byte of the first trace-header.
Raises:
ValueError: If the provided header data has the wrong shape.
UnicodeError: If the textual data could not be encoded into the specified encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing extended textual header",
encoding)
fh.seek(REEL_HEADER_NUM_BYTES)
encoded_pages = []
for page_index, page in enumerate(pages):
encoded_page = []
# TODO: Share some of this code with writing the textual reel header.
for line_index, line in enumerate(page):
encoded_line = line.encode(encoding)
num_encoded_bytes = len(encoded_line)
if num_encoded_bytes != CARD_LENGTH:
raise ValueError(
"Extended textual header line {} of page {} at {} bytes is not "
"{} bytes".format(line_index, page_index,
num_encoded_bytes, CARD_LENGTH))
encoded_page.append(encoded_line)
num_encoded_lines = len(encoded_page)
if num_encoded_lines != CARDS_PER_HEADER:
raise ValueError("Extended textual header page {} number of "
"lines {} is not {}".format(
page_index, num_encoded_lines,
CARDS_PER_HEADER))
encoded_pages.append(encoded_page),
for encoded_page in encoded_pages:
concatenated_page = EMPTY_BYTE_STRING.join(encoded_page)
assert (len(concatenated_page) == TEXTUAL_HEADER_NUM_BYTES)
fh.write(concatenated_page)
def write_segy(fh,
seg_y_data,
encoding=None,
trace_header_format=TraceHeaderRev1,
endian='>',
progress=None):
"""
Args:
fh: A file-like object open for binary write, positioned to write the textual reel header.
seg_y_data: An object from which the headers and trace_samples data can be retrieved. Requires the following
properties and methods:
seg_y_data.textual_reel_header
seg_y_data.binary_reel_header
seg_y_data.extended_textual_header
seg_y_data.trace_indexes
seg_y_data.trace_header(trace_index)
seg_y_data.trace_samples(trace_index)
seg_y_data.encoding
seg_y_data.endian
seg_y_data.data_sample_format
One such legitimate object would be a SegYReader instance.
trace_header_format: The class which defines the layout of the trace header. Defaults to TraceHeaderRev1.
encoding: Optional encoding for text data. Typically 'cp037' for EBCDIC or 'ascii' for ASCII. If omitted, the
seg_y_data object will be queries for an encoding property.
endian: Big endian by default. If omitted, the seg_y_data object will be queried for an encoding property.
progress: An optional progress bar object.
Raises:
UnsupportedEncodingError: If the specified encoding is neither ASCII nor EBCDIC
UnicodeError: If textual data provided cannot be encoded into the required encoding.
"""
encoding = encoding or (hasattr(seg_y_data, 'encoding') and seg_y_data.encoding) or ASCII
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, seg_y_data.textual_reel_header, encoding)
write_binary_reel_header(fh, seg_y_data.binary_reel_header, endian)
write_extended_textual_headers(fh, seg_y_data.extended_textual_header, encoding)
trace_header_packer = make_header_packer(trace_header_format, endian)
for trace_index in seg_y_data.trace_indexes():
write_trace_header(fh, seg_y_data.trace_header(trace_index), trace_header_packer)
write_trace_samples(fh, seg_y_data.trace_samples(trace_index), seg_y_data.data_sample_format, endian=endian)
def write_segy(fh,
dataset,
encoding=None,
trace_header_format=TraceHeaderRev1,
endian='>',
progress=None):
"""
Args:
fh: A file-like object open for binary write, positioned to write the textual reel header.
dataset: An object implementing the interface of segpy.dataset.Dataset, such as a SegYReader.
trace_header_format: The class which defines the layout of the trace header. Defaults to TraceHeaderRev1.
encoding: Optional encoding for text data. Typically 'cp037' for EBCDIC or 'ascii' for ASCII. If omitted, the
seg_y_data object will be queries for an encoding property.
endian: Big endian by default. If omitted, the dataset object will be queried for an encoding property.
progress: A unary callable which will be passed a number
between zero and one indicating the progress made. If
provided, this callback will be invoked at least once with
an argument equal to one.
Raises:
UnsupportedEncodingError: If the specified encoding is neither ASCII nor EBCDIC
UnicodeError: If textual data provided cannot be encoded into the required encoding.
"""
progress_callback = progress if progress is not None else lambda p: None
if not callable(progress_callback):
raise TypeError("write_segy(): progress callback must be callable")
encoding = encoding or (hasattr(dataset, 'encoding') and dataset.encoding) or ASCII
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, dataset.textual_reel_header, encoding)
write_binary_reel_header(fh, dataset.binary_reel_header, endian)
write_extended_textual_headers(fh, dataset.extended_textual_header, encoding)
trace_header_packer = make_header_packer(trace_header_format, endian)
num_traces = dataset.num_traces()
for trace_index in dataset.trace_indexes():
write_trace_header(fh, dataset.trace_header(trace_index), trace_header_packer)
write_trace_samples(fh, dataset.trace_samples(trace_index), dataset.data_sample_format, endian=endian)
progress_callback(trace_index / num_traces)
progress_callback(1)
def write_extended_textual_headers(fh, pages, encoding):
"""Write extended textual headers.
Args:
fh: A file-like object open in binary mode for writing.
pages: An iterables series of sequences of Unicode strings, where the outer iterable
represents 3200 byte pages, each comprised of a sequence of exactly 40 strings of nominally 80 characters
each. Although Unicode strings are accepted, and when encoded they should result in exact 80 bytes
sequences. To produce a valid data structure for pages, consider using format_extended_textual_header()
encoding: Either 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be position at the first byte after the extended textual headers, which is
also the first byte of the first trace-header.
Raises:
ValueError: If the provided header data has the wrong shape.
UnicodeError: If the textual data could not be encoded into the specified encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing extended textual header", encoding)
fh.seek(REEL_HEADER_NUM_BYTES)
encoded_pages = []
for page_index, page in enumerate(pages):
encoded_page = []
# TODO: Share some of this code with writing the textual reel header.
for line_index, line in enumerate(page):
encoded_line = line.encode(encoding)
num_encoded_bytes = len(encoded_line)
if num_encoded_bytes != CARD_LENGTH:
raise ValueError("Extended textual header line {} of page {} at {} bytes is not "
"{} bytes".format(line_index, page_index, num_encoded_bytes, CARD_LENGTH))
encoded_page.append(encoded_line)
num_encoded_lines = len(encoded_page)
if num_encoded_lines != CARDS_PER_HEADER:
raise ValueError("Extended textual header page {} number of "
"lines {} is not {}".format(num_encoded_lines, CARDS_PER_HEADER))
encoded_pages.append(encoded_page)
for encoded_page in encoded_pages:
concatenated_page = EMPTY_BYTE_STRING.join(encoded_page)
assert(len(concatenated_page) == TEXTUAL_HEADER_NUM_BYTES)
fh.write(concatenated_page)
def write_textual_reel_header(fh, lines, encoding):
"""Write the SEG Y card image header, also known as the textual header
Args:
fh: A file-like object open in binary mode positioned such that the
beginning of the textual header will be the next byte to read.
lines: An iterable series of forty lines, each of which must be a
Unicode string of CARD_LENGTH characters. The first three characters
of each line are often "C 1" to "C40" (as required by the SEG Y
standard) although this is not enforced by this function, since
many widespread SEG Y readers and writers do not adhere to this
constraint. To produce a SEG Y compliant series of header lines
consider using the format_standard_textual_header() function.
Any lines longer than CARD_LENGTH characters will be truncated without
warning. Any excess lines over CARDS_PER_HEADER will be discarded. Short
or omitted lines will be padded with spaces.
encoding: Typically 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be positioned at the first byte following the textual
header.
Raises:
UnsupportedEncodingError: If encoding is neither EBCDIC nor ASCII.
UnicodeError: If the data provided in lines cannot be encoded with the encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing textual reel header", encoding)
fh.seek(0)
padded_lines = [line.encode(encoding).ljust(CARD_LENGTH, ' '.encode(encoding))[:CARD_LENGTH]
for line in pad(lines, padding='', size=CARDS_PER_HEADER)]
joined_header = EMPTY_BYTE_STRING.join(padded_lines)
assert len(joined_header) == 3200
fh.write(joined_header)
fh.seek(TEXTUAL_HEADER_NUM_BYTES)
def write_textual_reel_header(fh, lines, encoding):
"""Write the SEG Y card image header, also known as the textual header
Args:
fh: A file-like object open in binary mode positioned such that the
beginning of the textual header will be the next byte to read.
lines: An iterable series of forty lines, each of which must be a
Unicode string of CARD_LENGTH characters. The first three characters
of each line are often "C 1" to "C40" (as required by the SEG Y
standard) although this is not enforced by this function, since
many widespread SEG Y readers and writers do not adhere to this
constraint. To produce a SEG Y compliant series of header lines
consider using the format_standard_textual_header() function.
Any lines longer than CARD_LENGTH characters will be truncated without
warning. Any excess lines over CARDS_PER_HEADER will be discarded. Short
or omitted lines will be padded with spaces.
encoding: Typically 'cp037' for EBCDIC or 'ascii' for ASCII.
Post-condition:
The file pointer in fh will be positioned at the first byte following the textual
header.
Raises:
UnsupportedEncodingError: If encoding is neither EBCDIC nor ASCII.
UnicodeError: If the data provided in lines cannot be encoded with the encoding.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing textual reel header", encoding)
fh.seek(0)
padded_lines = [line.encode(encoding).ljust(CARD_LENGTH, ' '.encode(encoding))[:CARD_LENGTH]
for line in pad(lines, padding='', size=CARDS_PER_HEADER)]
joined_header = EMPTY_BYTE_STRING.join(padded_lines)
assert len(joined_header) == 3200
fh.write(joined_header)
fh.seek(TEXTUAL_HEADER_NUM_BYTES)
def write_segy(fh,
dataset,
encoding=None,
trace_header_format=TraceHeaderRev1,
endian='>',
progress=None):
"""
Args:
fh: A file-like object open for binary write, positioned to write the textual reel header.
dataset: An object implementing the interface of segpy.dataset.Dataset, such as a SegYReader.
trace_header_format: The class which defines the layout of the trace header. Defaults to TraceHeaderRev1.
encoding: Optional encoding for text data. Typically 'cp037' for EBCDIC or 'ascii' for ASCII. If omitted, the
seg_y_data object will be queries for an encoding property.
endian: Big endian by default. If omitted, the seg_y_data object will be queried for an encoding property.
progress: An optional progress bar object.
Raises:
UnsupportedEncodingError: If the specified encoding is neither ASCII nor EBCDIC
UnicodeError: If textual data provided cannot be encoded into the required encoding.
"""
encoding = encoding or (hasattr(dataset, 'encoding') and dataset.encoding) or ASCII
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Writing SEG Y", encoding)
write_textual_reel_header(fh, dataset.textual_reel_header, encoding)
write_binary_reel_header(fh, dataset.binary_reel_header, endian)
write_extended_textual_headers(fh, dataset.extended_textual_header, encoding)
trace_header_packer = make_header_packer(trace_header_format, endian)
for trace_index in dataset.trace_indexes():
write_trace_header(fh, dataset.trace_header(trace_index), trace_header_packer)
write_trace_samples(fh, dataset.trace_samples(trace_index), dataset.data_sample_format, endian=endian)
def format_extended_textual_header(text, encoding, include_text_stop=False):
"""Format a string into pages and line suitable for an extended textual header.
Args
text: An arbitrary text string. Any universal newlines will be preserved.
encoding: Either ASCII ('ascii') or EBCDIC ('cp037')
include_text_stop: If True, a text stop stanza header will be appended, otherwise not.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Extended textual header", encoding)
# According to the standard: "The Extended Textual File Header consists of one or more 3200-byte records, each
# record containing 40 lines of textual card-image text." It goes on "... Each line in an Extended Textual File
# Header ends in carriage return and linefeed (EBCDIC 0D25 or ASCII 0D0A)." Given that we're dealing with fixed-
# length (80 byte) lines, this implies that we have 78 bytes of space into which we can encode the content of each
# line, which must be left-justified and padded with spaces.
width = CARD_LENGTH - len(HEADER_NEWLINE)
original_lines = text.splitlines()
# Split overly long lines (i.e. > 78) and pad too-short lines with spaces
lines = []
for original_line in original_lines:
padded_lines = (pad_and_terminate_header_line(
original_line[i:i + width], width)
for i in range(0, len(original_line), width))
lines.extend(padded_lines)
pages = list(batched(lines, 40, pad_and_terminate_header_line('', width)))
if include_text_stop:
stop_page = format_extended_textual_header(END_TEXT_STANZA,
encoding)[0]
pages.append(stop_page)
return pages
def format_extended_textual_header(text, encoding, include_text_stop=False):
"""Format a string into pages and line suitable for an extended textual header.
Args
text: An arbitrary text string. Any universal newlines will be preserved.
encoding: Either ASCII ('ascii') or EBCDIC ('cp037')
include_text_stop: If True, a text stop stanza header will be appended, otherwise not.
"""
if not is_supported_encoding(encoding):
raise UnsupportedEncodingError("Extended textual header", encoding)
# According to the standard: "The Extended Textual File Header consists of one or more 3200-byte records, each
# record containing 40 lines of textual card-image text." It goes on "... Each line in an Extended Textual File
# Header ends in carriage return and linefeed (EBCDIC 0D25 or ASCII 0D0A)." Given that we're dealing with fixed-
# length (80 byte) lines, this implies that we have 78 bytes of space into which we can encode the content of each
# line, which must be left-justified and padded with spaces.
width = CARD_LENGTH - len(HEADER_NEWLINE)
original_lines = text.splitlines()
# Split overly long lines (i.e. > 78) and pad too-short lines with spaces
lines = []
for original_line in original_lines:
padded_lines = (pad_and_terminate_header_line(original_line[i:i+width], width)
for i in range(0, len(original_line), width))
lines.extend(padded_lines)
pages = list(batched(lines, 40, pad_and_terminate_header_line('', width)))
if include_text_stop:
stop_page = format_extended_textual_header(END_TEXT_STANZA, encoding)[0]
pages.append(stop_page)
return pages
def test_unsupported_encoding_raises_unsupported_encoding_error(
self, encoding):
assume(not is_supported_encoding(encoding))
with raises(UnsupportedEncodingError):
toolkit.write_extended_textual_headers(None, [], encoding)
def test_unsupported_encoding_raises_unsupported_encoding_error(
self, encoding):
assume(not is_supported_encoding(encoding))
with raises(UnsupportedEncodingError):
toolkit.format_extended_textual_header('', encoding)
def test_unsupported_encoding_raises_unsupported_encoding_error(self, encoding):
assume(not is_supported_encoding(encoding))
with raises(UnsupportedEncodingError):
toolkit.write_extended_textual_headers(None, [], encoding)
def test_unsupported_encoding_raises_unsupported_encoding_error(self, encoding):
assume(not is_supported_encoding(encoding))
with raises(UnsupportedEncodingError):
toolkit.format_extended_textual_header('', encoding)