Branch
Hash :
ec2e58c1
Author :
Date :
2024-02-22T11:32:53
pngexif: Import pngexifinfo as an externally-contributed project
We used this experimental project in the development of the PNG-EXIF
("eXIf") specification, back in 2017. The project evolved together
with the draft specification, which was finalized on 2017-Jun-15 and
approved by the PNG Group on 2017-Jul-13.
The EXIF specification, outside of the scope of PNG and libpng, is
quite complex. The libpng implementation cannot grow too much beyond
performing basic integrity checks on top of serialization. In order
to create and manipulate PNG-EXIF image files, the use of external
libraries and tools such as ExifTool is necessary.
Now, with the addition of contrib/pngexif to the libpng repository,
offline tasks like metadata inspection and linting can be performed
without importing external dependencies.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306
#!/usr/bin/env python
"""
Show the EXIF information.
Copyright (C) 2017-2020 Cosmin Truta.
Use, modification and distribution are subject to the MIT License.
Please see the accompanying file LICENSE_MIT.txt
"""
from __future__ import absolute_import, division, print_function
import sys
from bytepack import (unpack_uint32be,
unpack_uint32le,
unpack_uint16be,
unpack_uint16le,
unpack_uint8)
# Generously allow the TIFF file to occupy up to a quarter-gigabyte.
# TODO: Reduce this limit to 64K and use file seeking for anything larger.
_READ_DATA_SIZE_MAX = 256 * 1024 * 1024
_TIFF_TAG_TYPES = {
1: "byte",
2: "ascii",
3: "short",
4: "long",
5: "rational",
6: "sbyte",
7: "undefined",
8: "sshort",
9: "slong",
10: "srational",
11: "float",
12: "double",
}
# See http://www.digitalpreservation.gov/formats/content/tiff_tags.shtml
_TIFF_TAGS = {
0x00fe: "Subfile Type",
0x0100: "Width",
0x0101: "Height",
0x0102: "Bits per Sample",
0x0103: "Compression",
0x0106: "Photometric",
0x010d: "Document Name",
0x010e: "Image Description",
0x010f: "Make",
0x0110: "Model",
0x0111: "Strip Offsets",
0x0112: "Orientation",
0x0115: "Samples per Pixel",
0x0116: "Rows per Strip",
0x0117: "Strip Byte Counts",
0x0118: "Min Sample Value",
0x0119: "Max Sample Value",
0x011a: "X Resolution",
0x011b: "Y Resolution",
0x011c: "Planar Configuration",
0x011d: "Page Name",
0x011e: "X Position",
0x011f: "Y Position",
0x0128: "Resolution Unit",
0x0129: "Page Number",
0x0131: "Software",
0x0132: "Date Time",
0x013b: "Artist",
0x013c: "Host Computer",
0x013d: "Predictor",
0x013e: "White Point",
0x013f: "Primary Chromaticities",
0x0140: "Color Map",
0x0141: "Half-Tone Hints",
0x0142: "Tile Width",
0x0143: "Tile Length",
0x0144: "Tile Offsets",
0x0145: "Tile Byte Counts",
0x0211: "YCbCr Coefficients",
0x0212: "YCbCr Subsampling",
0x0213: "YCbCr Positioning",
0x0214: "Reference Black White",
0x022f: "Strip Row Counts",
0x02bc: "XMP",
0x8298: "Copyright",
0x83bb: "IPTC",
0x8769: "EXIF IFD",
0x8773: "ICC Profile",
0x8825: "GPS IFD",
0xa005: "Interoperability IFD",
0xc4a5: "Print IM",
# EXIF IFD tags
0x829a: "Exposure Time",
0x829d: "F-Number",
0x8822: "Exposure Program",
0x8824: "Spectral Sensitivity",
0x8827: "ISO Speed Ratings",
0x8828: "OECF",
0x9000: "EXIF Version",
0x9003: "DateTime Original",
0x9004: "DateTime Digitized",
0x9101: "Components Configuration",
0x9102: "Compressed Bits Per Pixel",
0x9201: "Shutter Speed Value",
0x9202: "Aperture Value",
0x9203: "Brightness Value",
0x9204: "Exposure Bias Value",
0x9205: "Max Aperture Value",
0x9206: "Subject Distance",
0x9207: "Metering Mode",
0x9208: "Light Source",
0x9209: "Flash",
0x920a: "Focal Length",
0x9214: "Subject Area",
0x927c: "Maker Note",
0x9286: "User Comment",
# ... TODO
0xa000: "Flashpix Version",
0xa001: "Color Space",
0xa002: "Pixel X Dimension",
0xa003: "Pixel Y Dimension",
0xa004: "Related Sound File",
# ... TODO
# GPS IFD tags
# ... TODO
}
_TIFF_EXIF_IFD = 0x8769
_GPS_IFD = 0x8825
_INTEROPERABILITY_IFD = 0xa005
class ExifInfo:
"""EXIF reader and information lister."""
_endian = None
_buffer = None
_offset = 0
_global_ifd_offset = 0
_exif_ifd_offset = 0
_gps_ifd_offset = 0
_interoperability_ifd_offset = 0
_hex = False
def __init__(self, buffer, **kwargs):
"""Initialize the EXIF data reader."""
self._hex = kwargs.get("hex", False)
self._verbose = kwargs.get("verbose", False)
if not isinstance(buffer, bytes):
raise RuntimeError("invalid EXIF data type")
if buffer.startswith(b"MM\x00\x2a"):
self._endian = "MM"
elif buffer.startswith(b"II\x2a\x00"):
self._endian = "II"
else:
raise RuntimeError("invalid EXIF header")
self._buffer = buffer
self._offset = 4
self._global_ifd_offset = self._ui32()
def endian(self):
"""Return the endianness of the EXIF data."""
return self._endian
def _tags_for_ifd(self, ifd_offset):
"""Yield the tags found at the given TIFF IFD offset."""
if ifd_offset < 8:
raise RuntimeError("invalid TIFF IFD offset")
self._offset = ifd_offset
ifd_size = self._ui16()
for _ in range(0, ifd_size):
tag_id = self._ui16()
tag_type = self._ui16()
count = self._ui32()
value_or_offset = self._ui32()
if self._endian == "MM":
# FIXME:
# value_or_offset requires a fixup under big-endian encoding.
if tag_type == 2:
# 2 --> "ascii"
value_or_offset >>= 24
elif tag_type == 3:
# 3 --> "short"
value_or_offset >>= 16
else:
# ... FIXME
pass
if count == 0:
raise RuntimeError("unsupported count=0 in tag 0x%x" % tag_id)
if tag_id == _TIFF_EXIF_IFD:
if tag_type != 4:
raise RuntimeError("incorrect tag type for EXIF IFD")
self._exif_ifd_offset = value_or_offset
elif tag_id == _GPS_IFD:
if tag_type != 4:
raise RuntimeError("incorrect tag type for GPS IFD")
self._gps_ifd_offset = value_or_offset
elif tag_id == _INTEROPERABILITY_IFD:
if tag_type != 4:
raise RuntimeError("incorrect tag type for Interop IFD")
self._interoperability_ifd_offset = value_or_offset
yield (tag_id, tag_type, count, value_or_offset)
def tags(self):
"""Yield all TIFF/EXIF tags."""
if self._verbose:
print("TIFF IFD : 0x%08x" % self._global_ifd_offset)
for tag in self._tags_for_ifd(self._global_ifd_offset):
yield tag
if self._exif_ifd_offset > 0:
if self._verbose:
print("EXIF IFD : 0x%08x" % self._exif_ifd_offset)
for tag in self._tags_for_ifd(self._exif_ifd_offset):
yield tag
if self._gps_ifd_offset > 0:
if self._verbose:
print("GPS IFD : 0x%08x" % self._gps_ifd_offset)
for tag in self._tags_for_ifd(self._gps_ifd_offset):
yield tag
if self._interoperability_ifd_offset > 0:
if self._verbose:
print("Interoperability IFD : 0x%08x" %
self._interoperability_ifd_offset)
for tag in self._tags_for_ifd(self._interoperability_ifd_offset):
yield tag
def tagid2str(self, tag_id):
"""Return an informative string representation of a TIFF tag id."""
idstr = _TIFF_TAGS.get(tag_id, "[Unknown]")
if self._hex:
idnum = "0x%04x" % tag_id
else:
idnum = "%d" % tag_id
return "%s (%s)" % (idstr, idnum)
@staticmethod
def tagtype2str(tag_type):
"""Return an informative string representation of a TIFF tag type."""
typestr = _TIFF_TAG_TYPES.get(tag_type, "[unknown]")
return "%d:%s" % (tag_type, typestr)
def tag2str(self, tag_id, tag_type, count, value_or_offset):
"""Return an informative string representation of a TIFF tag tuple."""
return "%s (type=%s) (count=%d) : 0x%08x" \
% (self.tagid2str(tag_id), self.tagtype2str(tag_type), count,
value_or_offset)
def _ui32(self):
"""Decode a 32-bit unsigned int found at the current offset;
advance the offset by 4.
"""
if self._offset + 4 > len(self._buffer):
raise RuntimeError("out-of-bounds uint32 access in EXIF")
if self._endian == "MM":
result = unpack_uint32be(self._buffer, self._offset)
else:
result = unpack_uint32le(self._buffer, self._offset)
self._offset += 4
return result
def _ui16(self):
"""Decode a 16-bit unsigned int found at the current offset;
advance the offset by 2.
"""
if self._offset + 2 > len(self._buffer):
raise RuntimeError("out-of-bounds uint16 access in EXIF")
if self._endian == "MM":
result = unpack_uint16be(self._buffer, self._offset)
else:
result = unpack_uint16le(self._buffer, self._offset)
self._offset += 2
return result
def _ui8(self):
"""Decode an 8-bit unsigned int found at the current offset;
advance the offset by 1.
"""
if self._offset + 1 > len(self._buffer):
raise RuntimeError("out-of-bounds uint8 access in EXIF")
result = unpack_uint8(self._buffer, self._offset)
self._offset += 1
return result
def print_raw_exif_info(buffer, **kwargs):
"""Print the EXIF information found in a raw byte stream."""
lister = ExifInfo(buffer, **kwargs)
print("EXIF (endian=%s)" % lister.endian())
for (tag_id, tag_type, count, value_or_offset) in lister.tags():
print(lister.tag2str(tag_id=tag_id,
tag_type=tag_type,
count=count,
value_or_offset=value_or_offset))
if __name__ == "__main__":
# For testing only.
for arg in sys.argv[1:]:
with open(arg, "rb") as test_stream:
test_buffer = test_stream.read(_READ_DATA_SIZE_MAX)
print_raw_exif_info(test_buffer, hex=True, verbose=True)