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Steve Canny
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img: add _JfifMarkers.from_stream()
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Lines changed: 230 additions & 5 deletions

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‎docx/image/constants.py‎

Lines changed: 88 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,94 @@
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"""
66

77

8+
class JPEG_MARKER_CODE(object):
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"""
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JPEG marker codes
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"""
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TEM = b'\x01'
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DHT = b'\xC4'
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DAC = b'\xCC'
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JPG = b'\xC8'
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17+
SOF0 = b'\xC0'
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SOF1 = b'\xC1'
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SOF2 = b'\xC2'
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SOF3 = b'\xC3'
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SOF5 = b'\xC5'
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SOF6 = b'\xC6'
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SOF7 = b'\xC7'
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SOF9 = b'\xC9'
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SOFA = b'\xCA'
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SOFB = b'\xCB'
27+
SOFD = b'\xCD'
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SOFE = b'\xCE'
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SOFF = b'\xCF'
30+
31+
RST0 = b'\xD0'
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RST1 = b'\xD1'
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RST2 = b'\xD2'
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RST3 = b'\xD3'
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RST4 = b'\xD4'
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RST5 = b'\xD5'
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RST6 = b'\xD6'
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RST7 = b'\xD7'
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SOI = b'\xD8'
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EOI = b'\xD9'
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SOS = b'\xDA'
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DQT = b'\xDB' # Define Quantization Table(s)
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DNL = b'\xDC'
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DRI = b'\xDD'
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DHP = b'\xDE'
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EXP = b'\xDF'
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APP0 = b'\xE0'
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APP1 = b'\xE1'
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APP2 = b'\xE2'
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APP3 = b'\xE3'
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APP4 = b'\xE4'
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APP5 = b'\xE5'
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APP6 = b'\xE6'
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APP7 = b'\xE7'
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APP8 = b'\xE8'
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APP9 = b'\xE9'
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APPA = b'\xEA'
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APPB = b'\xEB'
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APPC = b'\xEC'
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APPD = b'\xED'
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APPE = b'\xEE'
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APPF = b'\xEF'
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66+
STANDALONE_MARKERS = (
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TEM, SOI, EOI, RST0, RST1, RST2, RST3, RST4, RST5, RST6, RST7
68+
)
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70+
SOF_MARKER_CODES = (
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SOF0, SOF1, SOF2, SOF3, SOF5, SOF6, SOF7, SOF9, SOFA, SOFB, SOFD,
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SOFE, SOFF
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)
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names = {
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b'\x00': 'UNKNOWN',
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b'\xC0': 'SOF0',
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b'\xC2': 'SOF2',
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b'\xC4': 'DHT',
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b'\xDA': 'SOS', # start of scan
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b'\xD8': 'SOI', # start of image
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b'\xD9': 'EOI', # end of image
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b'\xDB': 'DQT',
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b'\xE0': 'APP0',
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b'\xE1': 'APP1',
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b'\xE2': 'APP2',
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b'\xED': 'APP13',
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b'\xEE': 'APP14',
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}
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91+
@classmethod
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def is_standalone(cls, marker_code):
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return marker_code in cls.STANDALONE_MARKERS
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95+
896
class MIME_TYPE(object):
997
"""
1098
Image content types.

‎docx/image/jpeg.py‎

Lines changed: 62 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,7 @@
77

88
from __future__ import absolute_import, division, print_function
99

10+
from .constants import JPEG_MARKER_CODE
1011
from .image import Image
1112

1213

@@ -65,13 +66,23 @@ class _JfifMarkers(object):
6566
Sequence of markers in a JPEG file, perhaps truncated at first SOS marker
6667
for performance reasons.
6768
"""
69+
def __init__(self, markers):
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super(_JfifMarkers, self).__init__()
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self._markers = list(markers)
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6873
@classmethod
6974
def from_stream(cls, stream):
7075
"""
71-
Return a |_JfifMarkers| instance containing a |_JfifMarker| instance
72-
for each marker in *stream*.
76+
Return a |_JfifMarkers| instance containing a |_JfifMarker| subclass
77+
instance for each marker in *stream*.
7378
"""
74-
raise NotImplementedError
79+
marker_parser = _MarkerParser.from_stream(stream)
80+
markers = []
81+
for marker in marker_parser.iter_markers():
82+
markers.append(marker)
83+
if marker.marker_code == JPEG_MARKER_CODE.SOS:
84+
break
85+
return cls(markers)
7586

7687
@property
7788
def app0(self):
@@ -86,3 +97,51 @@ def sof(self):
8697
First start of frame (SOFn) marker in this sequence.
8798
"""
8899
raise NotImplementedError
100+
101+
102+
class _MarkerParser(object):
103+
"""
104+
Service class that knows how to parse a JFIF stream and iterate over its
105+
markers.
106+
"""
107+
@classmethod
108+
def from_stream(cls, stream):
109+
"""
110+
Return a |_MarkerParser| instance to parse JFIF markers from
111+
*stream*.
112+
"""
113+
raise NotImplementedError
114+
115+
def iter_markers(self):
116+
"""
117+
Generate a (marker_code, segment_offset) 3-tuple for each marker in
118+
the JPEG byte stream in *stream*, in the order they occur in the
119+
stream.
120+
"""
121+
raise NotImplementedError
122+
123+
124+
class _Marker(object):
125+
"""
126+
Base class for JFIF marker classes. Represents a marker and its segment
127+
occuring in a JPEG byte stream.
128+
"""
129+
@property
130+
def marker_code(self):
131+
"""
132+
The single-byte code that identifies the type of this marker, e.g.
133+
``'\xE0'`` for start of image (SOI).
134+
"""
135+
raise NotImplementedError
136+
137+
138+
class _App0Marker(_Marker):
139+
"""
140+
Represents a JFIF APP0 marker segment.
141+
"""
142+
143+
144+
class _SofMarker(_Marker):
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"""
146+
Represents a JFIF start of frame (SOFx) marker segment.
147+
"""

‎tests/image/test_jpeg.py‎

Lines changed: 80 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -9,9 +9,12 @@
99
import pytest
1010

1111
from docx.compat import BytesIO
12-
from docx.image.jpeg import Jfif, _JfifMarkers
12+
from docx.image.constants import JPEG_MARKER_CODE
13+
from docx.image.jpeg import (
14+
_App0Marker, Jfif, _JfifMarkers, _Marker, _MarkerParser, _SofMarker
15+
)
1316

14-
from ..unitutil import class_mock, instance_mock
17+
from ..unitutil import class_mock, initializer_mock, instance_mock
1518

1619

1720
class DescribeJfif(object):
@@ -67,3 +70,78 @@ def jfif_markers_(self, request):
6770
@pytest.fixture
6871
def stream_(self, request):
6972
return instance_mock(request, BytesIO)
73+
74+
75+
class Describe_JfifMarkers(object):
76+
77+
def it_can_construct_from_a_jfif_stream(self, from_stream_fixture):
78+
stream_, _MarkerParser_, _JfifMarkers__init_, marker_lst = (
79+
from_stream_fixture
80+
)
81+
jfif_markers = _JfifMarkers.from_stream(stream_)
82+
_MarkerParser_.from_stream.assert_called_once_with(stream_)
83+
_JfifMarkers__init_.assert_called_once_with(marker_lst)
84+
assert isinstance(jfif_markers, _JfifMarkers)
85+
86+
# fixtures -------------------------------------------------------
87+
88+
@pytest.fixture
89+
def app0_(self, request):
90+
return instance_mock(
91+
request, _App0Marker, marker_code=JPEG_MARKER_CODE.APP0
92+
)
93+
94+
@pytest.fixture
95+
def eoi_(self, request):
96+
return instance_mock(
97+
request, _SofMarker, marker_code=JPEG_MARKER_CODE.EOI
98+
)
99+
100+
@pytest.fixture
101+
def from_stream_fixture(
102+
self, stream_, _MarkerParser_, _JfifMarkers__init_, soi_, app0_,
103+
sof_, sos_):
104+
marker_lst = [soi_, app0_, sof_, sos_]
105+
return stream_, _MarkerParser_, _JfifMarkers__init_, marker_lst
106+
107+
@pytest.fixture
108+
def _JfifMarkers__init_(self, request):
109+
return initializer_mock(request, _JfifMarkers)
110+
111+
@pytest.fixture
112+
def marker_parser_(self, request, markers_all_):
113+
marker_parser_ = instance_mock(request, _MarkerParser)
114+
marker_parser_.iter_markers.return_value = markers_all_
115+
return marker_parser_
116+
117+
@pytest.fixture
118+
def _MarkerParser_(self, request, marker_parser_):
119+
_MarkerParser_ = class_mock(request, 'docx.image.jpeg._MarkerParser')
120+
_MarkerParser_.from_stream.return_value = marker_parser_
121+
return _MarkerParser_
122+
123+
@pytest.fixture
124+
def markers_all_(self, request, soi_, app0_, sof_, sos_, eoi_):
125+
return [soi_, app0_, sof_, sos_, eoi_]
126+
127+
@pytest.fixture
128+
def sof_(self, request):
129+
return instance_mock(
130+
request, _SofMarker, marker_code=JPEG_MARKER_CODE.SOF0
131+
)
132+
133+
@pytest.fixture
134+
def soi_(self, request):
135+
return instance_mock(
136+
request, _Marker, marker_code=JPEG_MARKER_CODE.SOI
137+
)
138+
139+
@pytest.fixture
140+
def sos_(self, request):
141+
return instance_mock(
142+
request, _Marker, marker_code=JPEG_MARKER_CODE.SOS
143+
)
144+
145+
@pytest.fixture
146+
def stream_(self, request):
147+
return instance_mock(request, BytesIO)

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