Finished refactoring marker segment parsing, #94.
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John Evans
parent
2b5b1d081d
commit
ebb15b0fba
2 changed files with 76 additions and 79 deletions
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@ -77,6 +77,66 @@ class Codestream(object):
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If True, only marker segments in the main header are parsed.
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Supplying False may impose a large performance penalty.
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"""
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# Map each of the known markers to a method that processes them.
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process_marker_segment = {
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0xff00: self._parse_reserved_segment,
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0xff01: self._parse_reserved_segment,
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0xff30: self._parse_reserved_marker,
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0xff31: self._parse_reserved_marker,
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0xff32: self._parse_reserved_marker,
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0xff33: self._parse_reserved_marker,
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0xff34: self._parse_reserved_marker,
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0xff35: self._parse_reserved_marker,
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0xff36: self._parse_reserved_marker,
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0xff37: self._parse_reserved_marker,
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0xff38: self._parse_reserved_marker,
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0xff39: self._parse_reserved_marker,
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0xff3a: self._parse_reserved_marker,
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0xff3b: self._parse_reserved_marker,
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0xff3c: self._parse_reserved_marker,
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0xff3d: self._parse_reserved_marker,
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0xff3e: self._parse_reserved_marker,
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0xff3f: self._parse_reserved_marker,
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0xff4f: self._parse_reserved_segment,
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0xff50: self._parse_reserved_segment,
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0xff51: self._parse_siz_segment,
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0xff52: self._parse_cod_segment,
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0xff53: self._parse_coc_segment,
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0xff54: self._parse_reserved_segment,
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0xff55: self._parse_tlm_segment,
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0xff56: self._parse_reserved_segment,
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0xff57: self._parse_reserved_segment,
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0xff58: self._parse_plt_segment,
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0xff59: self._parse_reserved_segment,
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0xff5a: self._parse_reserved_segment,
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0xff5b: self._parse_reserved_segment,
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0xff5c: self._parse_qcd_segment,
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0xff5d: self._parse_qcc_segment,
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0xff5e: self._parse_rgn_segment,
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0xff5f: self._parse_pod_segment,
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0xff60: self._parse_ppm_segment,
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0xff61: self._parse_ppt_segment,
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0xff62: self._parse_reserved_segment,
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0xff63: self._parse_crg_segment,
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0xff64: self._parse_cme_segment,
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0xff65: self._parse_reserved_segment,
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0xff66: self._parse_reserved_segment,
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0xff67: self._parse_reserved_segment,
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0xff68: self._parse_reserved_segment,
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0xff69: self._parse_reserved_segment,
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0xff6a: self._parse_reserved_segment,
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0xff6b: self._parse_reserved_segment,
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0xff6c: self._parse_reserved_segment,
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0xff6d: self._parse_reserved_segment,
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0xff6e: self._parse_reserved_segment,
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0xff6f: self._parse_reserved_segment,
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0xff79: self._parse_unrecognized_segment,
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0xff90: self._parse_sot_segment,
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0xff91: self._parse_unrecognized_segment,
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0xff92: self._parse_unrecognized_segment,
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0xff93: self._parse_sod_segment,
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0xffd9: self._parse_eoc_segment,
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}
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self.offset = fptr.tell()
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self.length = length
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@ -119,7 +179,13 @@ class Codestream(object):
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break
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try:
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segment = self._process_marker_segment(fptr)
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segment = process_marker_segment[self._marker_id](fptr)
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except KeyError:
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msg = 'Invalid marker id encountered at byte {0:d} '
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msg += 'in codestream: "0x{1:x}"'
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msg = msg.format(self._offset, self._marker_id)
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warnings.warn(msg)
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break
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except Exception as error:
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# Treat this as a warning.
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msg = str(error)
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@ -142,78 +208,9 @@ class Codestream(object):
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fptr.seek(self._tile_offset[-1] + self._tile_length[-1])
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def _process_marker_segment(self, fptr):
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"""Process and return a segment from the codestream.
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"""
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if self._marker_id >= 0xff30 and self._marker_id <= 0xff3f:
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segment = self._parse_reserved_marker(fptr)
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elif self._marker_id == 0xff51:
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segment = self._parse_siz_segment(fptr)
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elif self._marker_id == 0xff52:
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segment = self._parse_cod_segment(fptr)
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elif self._marker_id == 0xff53:
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segment = self._parse_coc_segment(fptr)
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elif self._marker_id == 0xff55:
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segment = self._parse_tlm_segment(fptr)
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elif self._marker_id == 0xff58:
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segment = self._parse_plt_segment(fptr)
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elif self._marker_id == 0xff5c:
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segment = self._parse_qcd_segment(fptr)
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elif self._marker_id == 0xff5d:
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segment = self._parse_qcc_segment(fptr)
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elif self._marker_id == 0xff5e:
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segment = self._parse_rgn_segment(fptr)
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elif self._marker_id == 0xff5f:
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segment = self._parse_pod_segment(fptr)
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elif self._marker_id == 0xff60:
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segment = self._parse_ppm_segment(fptr)
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elif self._marker_id == 0xff61:
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segment = self._parse_ppt_segment(fptr)
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elif self._marker_id == 0xff63:
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segment = self._parse_crg_segment(fptr)
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elif self._marker_id == 0xff64:
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segment = self._parse_cme_segment(fptr)
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elif self._marker_id == 0xff90:
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segment = self._parse_sot_segment(fptr)
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elif self._marker_id == 0xff93:
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segment = self._parse_sod_segment(fptr)
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elif self._marker_id == 0xffd9:
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segment = self._parse_eoc_segment(fptr)
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elif self._marker_id in _VALID_MARKERS:
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# It's a reserved marker that I don't know anything about.
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# See table A-1 in ISO/IEC FCD15444-1.
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segment = self._parse_reserved_segment(fptr)
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elif self._marker_id == 0xff79:
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segment = self._parse_unrecognized_segment(fptr)
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else:
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msg = 'Invalid marker id encountered at byte {0:d} '
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msg += 'in codestream: "0x{1:x}"'
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msg = msg.format(self._offset, self._marker_id)
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raise IOError(msg)
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return segment
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def _parse_unrecognized_segment(self, fptr):
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"""Looks like a marker, but not sure what it is.
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"""Looks like a valid marker, but not sure from reading the specs.
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"""
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msg = "Unrecognized marker id: 0x{0:x}".format(self._marker_id)
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warnings.warn(msg)
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@ -240,7 +237,7 @@ class Codestream(object):
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def _parse_reserved_segment(self, fptr):
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"""Parse a marker segment for which we know nothing of the segment itself.
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"""Parse valid marker segment, segment description is unknown.
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Parameters
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----------
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@ -63,9 +63,9 @@ class TestCodestream(unittest.TestCase):
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self.assertEqual(c.segment[2].length, 3)
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self.assertEqual(c.segment[2]._data, b'\x00')
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@unittest.skipIf(os.name == "nt", "Temporary file issue on window.")
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@unittest.skipIf(sys.hexversion < 0x03020000,
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"Uses features introduced in 3.2.")
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@unittest.skipIf(os.name == "nt", "Temporary file issue on window.")
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def test_unknown_marker_segment(self):
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# Let's inject a marker segment whose marker does not appear to
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# be valid. We still parse the file, but warn about the offending
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@ -86,13 +86,13 @@ class TestCodestream(unittest.TestCase):
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tfile.write(buffer)
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tfile.flush()
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with self.assertWarns(UserWarning) as cw:
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j = Jp2k(tfile.name)
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c = j.get_codestream()
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with self.assertWarns(UserWarning):
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j = Jp2k(tfile.name)
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c = j.get_codestream()
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self.assertEqual(c.segment[2].marker_id, '0xff79')
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self.assertEqual(c.segment[2].length, 3)
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self.assertEqual(c.segment[2]._data, b'\x00')
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self.assertEqual(c.segment[2].marker_id, '0xff79')
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self.assertEqual(c.segment[2].length, 3)
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self.assertEqual(c.segment[2]._data, b'\x00')
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def test_psot_is_zero(self):
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# Psot=0 in SOT is perfectly legal. Issue #78.
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