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Finished refactoring marker segment parsing, #94.

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John Evans 2013-08-01 13:51:23 -04:00
commit ebb15b0fba
2 changed files with 76 additions and 79 deletions
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141
glymur/codestream.py
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@ -77,6 +77,66 @@ class Codestream(object):
If True, only marker segments in the main header are parsed. If True, only marker segments in the main header are parsed.
Supplying False may impose a large performance penalty. Supplying False may impose a large performance penalty.
""" """
# Map each of the known markers to a method that processes them.
process_marker_segment = {
0xff00: self._parse_reserved_segment,
0xff01: self._parse_reserved_segment,
0xff30: self._parse_reserved_marker,
0xff31: self._parse_reserved_marker,
0xff32: self._parse_reserved_marker,
0xff33: self._parse_reserved_marker,
0xff34: self._parse_reserved_marker,
0xff35: self._parse_reserved_marker,
0xff36: self._parse_reserved_marker,
0xff37: self._parse_reserved_marker,
0xff38: self._parse_reserved_marker,
0xff39: self._parse_reserved_marker,
0xff3a: self._parse_reserved_marker,
0xff3b: self._parse_reserved_marker,
0xff3c: self._parse_reserved_marker,
0xff3d: self._parse_reserved_marker,
0xff3e: self._parse_reserved_marker,
0xff3f: self._parse_reserved_marker,
0xff4f: self._parse_reserved_segment,
0xff50: self._parse_reserved_segment,
0xff51: self._parse_siz_segment,
0xff52: self._parse_cod_segment,
0xff53: self._parse_coc_segment,
0xff54: self._parse_reserved_segment,
0xff55: self._parse_tlm_segment,
0xff56: self._parse_reserved_segment,
0xff57: self._parse_reserved_segment,
0xff58: self._parse_plt_segment,
0xff59: self._parse_reserved_segment,
0xff5a: self._parse_reserved_segment,
0xff5b: self._parse_reserved_segment,
0xff5c: self._parse_qcd_segment,
0xff5d: self._parse_qcc_segment,
0xff5e: self._parse_rgn_segment,
0xff5f: self._parse_pod_segment,
0xff60: self._parse_ppm_segment,
0xff61: self._parse_ppt_segment,
0xff62: self._parse_reserved_segment,
0xff63: self._parse_crg_segment,
0xff64: self._parse_cme_segment,
0xff65: self._parse_reserved_segment,
0xff66: self._parse_reserved_segment,
0xff67: self._parse_reserved_segment,
0xff68: self._parse_reserved_segment,
0xff69: self._parse_reserved_segment,
0xff6a: self._parse_reserved_segment,
0xff6b: self._parse_reserved_segment,
0xff6c: self._parse_reserved_segment,
0xff6d: self._parse_reserved_segment,
0xff6e: self._parse_reserved_segment,
0xff6f: self._parse_reserved_segment,
0xff79: self._parse_unrecognized_segment,
0xff90: self._parse_sot_segment,
0xff91: self._parse_unrecognized_segment,
0xff92: self._parse_unrecognized_segment,
0xff93: self._parse_sod_segment,
0xffd9: self._parse_eoc_segment,
}
self.offset = fptr.tell() self.offset = fptr.tell()
self.length = length self.length = length
@ -119,7 +179,13 @@ class Codestream(object):
break break
try: try:
segment = self._process_marker_segment(fptr) segment = process_marker_segment[self._marker_id](fptr)
except KeyError:
msg = 'Invalid marker id encountered at byte {0:d} '
msg += 'in codestream: "0x{1:x}"'
msg = msg.format(self._offset, self._marker_id)
warnings.warn(msg)
break
except Exception as error: except Exception as error:
# Treat this as a warning. # Treat this as a warning.
msg = str(error) msg = str(error)
@ -142,78 +208,9 @@ class Codestream(object):
fptr.seek(self._tile_offset[-1] + self._tile_length[-1]) fptr.seek(self._tile_offset[-1] + self._tile_length[-1])
def _process_marker_segment(self, fptr):
"""Process and return a segment from the codestream.
"""
if self._marker_id >= 0xff30 and self._marker_id <= 0xff3f:
segment = self._parse_reserved_marker(fptr)
elif self._marker_id == 0xff51:
segment = self._parse_siz_segment(fptr)
elif self._marker_id == 0xff52:
segment = self._parse_cod_segment(fptr)
elif self._marker_id == 0xff53:
segment = self._parse_coc_segment(fptr)
elif self._marker_id == 0xff55:
segment = self._parse_tlm_segment(fptr)
elif self._marker_id == 0xff58:
segment = self._parse_plt_segment(fptr)
elif self._marker_id == 0xff5c:
segment = self._parse_qcd_segment(fptr)
elif self._marker_id == 0xff5d:
segment = self._parse_qcc_segment(fptr)
elif self._marker_id == 0xff5e:
segment = self._parse_rgn_segment(fptr)
elif self._marker_id == 0xff5f:
segment = self._parse_pod_segment(fptr)
elif self._marker_id == 0xff60:
segment = self._parse_ppm_segment(fptr)
elif self._marker_id == 0xff61:
segment = self._parse_ppt_segment(fptr)
elif self._marker_id == 0xff63:
segment = self._parse_crg_segment(fptr)
elif self._marker_id == 0xff64:
segment = self._parse_cme_segment(fptr)
elif self._marker_id == 0xff90:
segment = self._parse_sot_segment(fptr)
elif self._marker_id == 0xff93:
segment = self._parse_sod_segment(fptr)
elif self._marker_id == 0xffd9:
segment = self._parse_eoc_segment(fptr)
elif self._marker_id in _VALID_MARKERS:
# It's a reserved marker that I don't know anything about.
# See table A-1 in ISO/IEC FCD15444-1.
segment = self._parse_reserved_segment(fptr)
elif self._marker_id == 0xff79:
segment = self._parse_unrecognized_segment(fptr)
else:
msg = 'Invalid marker id encountered at byte {0:d} '
msg += 'in codestream: "0x{1:x}"'
msg = msg.format(self._offset, self._marker_id)
raise IOError(msg)
return segment
def _parse_unrecognized_segment(self, fptr): def _parse_unrecognized_segment(self, fptr):
"""Looks like a marker, but not sure what it is. """Looks like a valid marker, but not sure from reading the specs.
""" """
msg = "Unrecognized marker id: 0x{0:x}".format(self._marker_id) msg = "Unrecognized marker id: 0x{0:x}".format(self._marker_id)
warnings.warn(msg) warnings.warn(msg)
@ -240,7 +237,7 @@ class Codestream(object):
def _parse_reserved_segment(self, fptr): def _parse_reserved_segment(self, fptr):
"""Parse a marker segment for which we know nothing of the segment itself. """Parse valid marker segment, segment description is unknown.
Parameters Parameters
---------- ----------

14
glymur/test/test_codestream.py
View file

@ -63,9 +63,9 @@ class TestCodestream(unittest.TestCase):
self.assertEqual(c.segment[2].length, 3) self.assertEqual(c.segment[2].length, 3)
self.assertEqual(c.segment[2]._data, b'\x00') self.assertEqual(c.segment[2]._data, b'\x00')
@unittest.skipIf(os.name == "nt", "Temporary file issue on window.")
@unittest.skipIf(sys.hexversion < 0x03020000, @unittest.skipIf(sys.hexversion < 0x03020000,
"Uses features introduced in 3.2.") "Uses features introduced in 3.2.")
@unittest.skipIf(os.name == "nt", "Temporary file issue on window.")
def test_unknown_marker_segment(self): def test_unknown_marker_segment(self):
# Let's inject a marker segment whose marker does not appear to # Let's inject a marker segment whose marker does not appear to
# be valid. We still parse the file, but warn about the offending # be valid. We still parse the file, but warn about the offending
@ -86,13 +86,13 @@ class TestCodestream(unittest.TestCase):
tfile.write(buffer) tfile.write(buffer)
tfile.flush() tfile.flush()
with self.assertWarns(UserWarning) as cw: with self.assertWarns(UserWarning):
j = Jp2k(tfile.name) j = Jp2k(tfile.name)
c = j.get_codestream() c = j.get_codestream()
self.assertEqual(c.segment[2].marker_id, '0xff79') self.assertEqual(c.segment[2].marker_id, '0xff79')
self.assertEqual(c.segment[2].length, 3) self.assertEqual(c.segment[2].length, 3)
self.assertEqual(c.segment[2]._data, b'\x00') self.assertEqual(c.segment[2]._data, b'\x00')
def test_psot_is_zero(self): def test_psot_is_zero(self):
# Psot=0 in SOT is perfectly legal. Issue #78. # Psot=0 in SOT is perfectly legal. Issue #78.