MediaWiki REL1_34
PNGMetadataExtractor.php
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1<?php
35 private static $pngSig;
36
38 private static $crcSize;
39
41 private static $textChunks;
42
43 const VERSION = 1;
44 const MAX_CHUNK_SIZE = 3145728; // 3 megabytes
45
46 static function getMetadata( $filename ) {
47 self::$pngSig = pack( "C8", 137, 80, 78, 71, 13, 10, 26, 10 );
48 self::$crcSize = 4;
49 /* based on list at http://owl.phy.queensu.ca/~phil/exiftool/TagNames/PNG.html#TextualData
50 * and https://www.w3.org/TR/PNG/#11keywords
51 */
52 self::$textChunks = [
53 'xml:com.adobe.xmp' => 'xmp',
54 # Artist is unofficial. Author is the recommended
55 # keyword in the PNG spec. However some people output
56 # Artist so support both.
57 'artist' => 'Artist',
58 'model' => 'Model',
59 'make' => 'Make',
60 'author' => 'Artist',
61 'comment' => 'PNGFileComment',
62 'description' => 'ImageDescription',
63 'title' => 'ObjectName',
64 'copyright' => 'Copyright',
65 # Source as in original device used to make image
66 # not as in who gave you the image
67 'source' => 'Model',
68 'software' => 'Software',
69 'disclaimer' => 'Disclaimer',
70 'warning' => 'ContentWarning',
71 'url' => 'Identifier', # Not sure if this is best mapping. Maybe WebStatement.
72 'label' => 'Label',
73 'creation time' => 'DateTimeDigitized',
74 /* Other potentially useful things - Document */
75 ];
76
77 $frameCount = 0;
78 $loopCount = 1;
79 $text = [];
80 $duration = 0.0;
81 $bitDepth = 0;
82 $colorType = 'unknown';
83
84 if ( !$filename ) {
85 throw new Exception( __METHOD__ . ": No file name specified" );
86 } elseif ( !file_exists( $filename ) || is_dir( $filename ) ) {
87 throw new Exception( __METHOD__ . ": File $filename does not exist" );
88 }
89
90 $fh = fopen( $filename, 'rb' );
91
92 if ( !$fh ) {
93 throw new Exception( __METHOD__ . ": Unable to open file $filename" );
94 }
95
96 // Check for the PNG header
97 $buf = fread( $fh, 8 );
98 if ( $buf != self::$pngSig ) {
99 throw new Exception( __METHOD__ . ": Not a valid PNG file; header: $buf" );
100 }
101
102 // Read chunks
103 while ( !feof( $fh ) ) {
104 $buf = fread( $fh, 4 );
105 if ( !$buf || strlen( $buf ) < 4 ) {
106 throw new Exception( __METHOD__ . ": Read error" );
107 }
108 $chunk_size = unpack( "N", $buf )[1];
109
110 if ( $chunk_size < 0 ) {
111 throw new Exception( __METHOD__ . ": Chunk size too big for unpack" );
112 }
113
114 $chunk_type = fread( $fh, 4 );
115 if ( !$chunk_type || strlen( $chunk_type ) < 4 ) {
116 throw new Exception( __METHOD__ . ": Read error" );
117 }
118
119 if ( $chunk_type == "IHDR" ) {
120 $buf = self::read( $fh, $chunk_size );
121 if ( !$buf || strlen( $buf ) < $chunk_size ) {
122 throw new Exception( __METHOD__ . ": Read error" );
123 }
124 $width = unpack( 'N', substr( $buf, 0, 4 ) )[1];
125 $height = unpack( 'N', substr( $buf, 4, 4 ) )[1];
126 $bitDepth = ord( substr( $buf, 8, 1 ) );
127 // Detect the color type in British English as per the spec
128 // https://www.w3.org/TR/PNG/#11IHDR
129 switch ( ord( substr( $buf, 9, 1 ) ) ) {
130 case 0:
131 $colorType = 'greyscale';
132 break;
133 case 2:
134 $colorType = 'truecolour';
135 break;
136 case 3:
137 $colorType = 'index-coloured';
138 break;
139 case 4:
140 $colorType = 'greyscale-alpha';
141 break;
142 case 6:
143 $colorType = 'truecolour-alpha';
144 break;
145 default:
146 $colorType = 'unknown';
147 break;
148 }
149 } elseif ( $chunk_type == "acTL" ) {
150 $buf = fread( $fh, $chunk_size );
151 if ( !$buf || strlen( $buf ) < $chunk_size || $chunk_size < 4 ) {
152 throw new Exception( __METHOD__ . ": Read error" );
153 }
154
155 $actl = unpack( "Nframes/Nplays", $buf );
156 $frameCount = $actl['frames'];
157 $loopCount = $actl['plays'];
158 } elseif ( $chunk_type == "fcTL" ) {
159 $buf = self::read( $fh, $chunk_size );
160 if ( !$buf || strlen( $buf ) < $chunk_size ) {
161 throw new Exception( __METHOD__ . ": Read error" );
162 }
163 $buf = substr( $buf, 20 );
164 if ( strlen( $buf ) < 4 ) {
165 throw new Exception( __METHOD__ . ": Read error" );
166 }
167
168 $fctldur = unpack( "ndelay_num/ndelay_den", $buf );
169 if ( $fctldur['delay_den'] == 0 ) {
170 $fctldur['delay_den'] = 100;
171 }
172 if ( $fctldur['delay_num'] ) {
173 $duration += $fctldur['delay_num'] / $fctldur['delay_den'];
174 }
175 } elseif ( $chunk_type == "iTXt" ) {
176 // Extracts iTXt chunks, uncompressing if necessary.
177 $buf = self::read( $fh, $chunk_size );
178 $items = [];
179 if ( preg_match(
180 '/^([^\x00]{1,79})\x00(\x00|\x01)\x00([^\x00]*)(.)[^\x00]*\x00(.*)$/Ds',
181 $buf, $items )
182 ) {
183 /* $items[1] = text chunk name, $items[2] = compressed flag,
184 * $items[3] = lang code (or ""), $items[4]= compression type.
185 * $items[5] = content
186 */
187
188 // Theoretically should be case-sensitive, but in practise...
189 $items[1] = strtolower( $items[1] );
190 if ( !isset( self::$textChunks[$items[1]] ) ) {
191 // Only extract textual chunks on our list.
192 fseek( $fh, self::$crcSize, SEEK_CUR );
193 continue;
194 }
195
196 $items[3] = strtolower( $items[3] );
197 if ( $items[3] == '' ) {
198 // if no lang specified use x-default like in xmp.
199 $items[3] = 'x-default';
200 }
201
202 // if compressed
203 if ( $items[2] == "\x01" ) {
204 if ( function_exists( 'gzuncompress' ) && $items[4] === "\x00" ) {
205 Wikimedia\suppressWarnings();
206 $items[5] = gzuncompress( $items[5] );
207 Wikimedia\restoreWarnings();
208
209 if ( $items[5] === false ) {
210 // decompression failed
211 wfDebug( __METHOD__ . ' Error decompressing iTxt chunk - ' . $items[1] . "\n" );
212 fseek( $fh, self::$crcSize, SEEK_CUR );
213 continue;
214 }
215 } else {
216 wfDebug( __METHOD__ . ' Skipping compressed png iTXt chunk due to lack of zlib,'
217 . " or potentially invalid compression method\n" );
218 fseek( $fh, self::$crcSize, SEEK_CUR );
219 continue;
220 }
221 }
222 $finalKeyword = self::$textChunks[$items[1]];
223 $text[$finalKeyword][$items[3]] = $items[5];
224 $text[$finalKeyword]['_type'] = 'lang';
225 } else {
226 // Error reading iTXt chunk
227 throw new Exception( __METHOD__ . ": Read error on iTXt chunk" );
228 }
229 } elseif ( $chunk_type == 'tEXt' ) {
230 $buf = self::read( $fh, $chunk_size );
231
232 // In case there is no \x00 which will make explode fail.
233 if ( strpos( $buf, "\x00" ) === false ) {
234 throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
235 }
236
237 list( $keyword, $content ) = explode( "\x00", $buf, 2 );
238 if ( $keyword === '' || $content === '' ) {
239 throw new Exception( __METHOD__ . ": Read error on tEXt chunk" );
240 }
241
242 // Theoretically should be case-sensitive, but in practise...
243 $keyword = strtolower( $keyword );
244 if ( !isset( self::$textChunks[$keyword] ) ) {
245 // Don't recognize chunk, so skip.
246 fseek( $fh, self::$crcSize, SEEK_CUR );
247 continue;
248 }
249 Wikimedia\suppressWarnings();
250 $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
251 Wikimedia\restoreWarnings();
252
253 if ( $content === false ) {
254 throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
255 }
256
257 $finalKeyword = self::$textChunks[$keyword];
258 $text[$finalKeyword]['x-default'] = $content;
259 $text[$finalKeyword]['_type'] = 'lang';
260 } elseif ( $chunk_type == 'zTXt' ) {
261 if ( function_exists( 'gzuncompress' ) ) {
262 $buf = self::read( $fh, $chunk_size );
263
264 // In case there is no \x00 which will make explode fail.
265 if ( strpos( $buf, "\x00" ) === false ) {
266 throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
267 }
268
269 list( $keyword, $postKeyword ) = explode( "\x00", $buf, 2 );
270 if ( $keyword === '' || $postKeyword === '' ) {
271 throw new Exception( __METHOD__ . ": Read error on zTXt chunk" );
272 }
273 // Theoretically should be case-sensitive, but in practise...
274 $keyword = strtolower( $keyword );
275
276 if ( !isset( self::$textChunks[$keyword] ) ) {
277 // Don't recognize chunk, so skip.
278 fseek( $fh, self::$crcSize, SEEK_CUR );
279 continue;
280 }
281 $compression = substr( $postKeyword, 0, 1 );
282 $content = substr( $postKeyword, 1 );
283 if ( $compression !== "\x00" ) {
284 wfDebug( __METHOD__ . " Unrecognized compression method in zTXt ($keyword). Skipping.\n" );
285 fseek( $fh, self::$crcSize, SEEK_CUR );
286 continue;
287 }
288
289 Wikimedia\suppressWarnings();
290 $content = gzuncompress( $content );
291 Wikimedia\restoreWarnings();
292
293 if ( $content === false ) {
294 // decompression failed
295 wfDebug( __METHOD__ . ' Error decompressing zTXt chunk - ' . $keyword . "\n" );
296 fseek( $fh, self::$crcSize, SEEK_CUR );
297 continue;
298 }
299
300 Wikimedia\suppressWarnings();
301 $content = iconv( 'ISO-8859-1', 'UTF-8', $content );
302 Wikimedia\restoreWarnings();
303
304 if ( $content === false ) {
305 throw new Exception( __METHOD__ . ": Read error (error with iconv)" );
306 }
307
308 $finalKeyword = self::$textChunks[$keyword];
309 $text[$finalKeyword]['x-default'] = $content;
310 $text[$finalKeyword]['_type'] = 'lang';
311 } else {
312 wfDebug( __METHOD__ . " Cannot decompress zTXt chunk due to lack of zlib. Skipping.\n" );
313 fseek( $fh, $chunk_size, SEEK_CUR );
314 }
315 } elseif ( $chunk_type == 'tIME' ) {
316 // last mod timestamp.
317 if ( $chunk_size !== 7 ) {
318 throw new Exception( __METHOD__ . ": tIME wrong size" );
319 }
320 $buf = self::read( $fh, $chunk_size );
321 if ( !$buf || strlen( $buf ) < $chunk_size ) {
322 throw new Exception( __METHOD__ . ": Read error" );
323 }
324
325 // Note: spec says this should be UTC.
326 $t = unpack( "ny/Cm/Cd/Ch/Cmin/Cs", $buf );
327 $strTime = sprintf( "%04d%02d%02d%02d%02d%02d",
328 $t['y'], $t['m'], $t['d'], $t['h'],
329 $t['min'], $t['s'] );
330
331 $exifTime = wfTimestamp( TS_EXIF, $strTime );
332
333 if ( $exifTime ) {
334 $text['DateTime'] = $exifTime;
335 }
336 } elseif ( $chunk_type == 'pHYs' ) {
337 // how big pixels are (dots per meter).
338 if ( $chunk_size !== 9 ) {
339 throw new Exception( __METHOD__ . ": pHYs wrong size" );
340 }
341
342 $buf = self::read( $fh, $chunk_size );
343 if ( !$buf || strlen( $buf ) < $chunk_size ) {
344 throw new Exception( __METHOD__ . ": Read error" );
345 }
346
347 $dim = unpack( "Nwidth/Nheight/Cunit", $buf );
348 if ( $dim['unit'] == 1 ) {
349 // Need to check for negative because php
350 // doesn't deal with super-large unsigned 32-bit ints well
351 if ( $dim['width'] > 0 && $dim['height'] > 0 ) {
352 // unit is meters
353 // (as opposed to 0 = undefined )
354 $text['XResolution'] = $dim['width']
355 . '/100';
356 $text['YResolution'] = $dim['height']
357 . '/100';
358 $text['ResolutionUnit'] = 3;
359 // 3 = dots per cm (from Exif).
360 }
361 }
362 } elseif ( $chunk_type == "IEND" ) {
363 break;
364 } else {
365 fseek( $fh, $chunk_size, SEEK_CUR );
366 }
367 fseek( $fh, self::$crcSize, SEEK_CUR );
368 }
369 fclose( $fh );
370
371 if ( $loopCount > 1 ) {
372 $duration *= $loopCount;
373 }
374
375 if ( isset( $text['DateTimeDigitized'] ) ) {
376 // Convert date format from rfc2822 to exif.
377 foreach ( $text['DateTimeDigitized'] as $name => &$value ) {
378 if ( $name === '_type' ) {
379 continue;
380 }
381
382 // @todo FIXME: Currently timezones are ignored.
383 // possibly should be wfTimestamp's
384 // responsibility. (at least for numeric TZ)
385 $formatted = wfTimestamp( TS_EXIF, $value );
386 if ( $formatted ) {
387 // Only change if we could convert the
388 // date.
389 // The png standard says it should be
390 // in rfc2822 format, but not required.
391 // In general for the exif stuff we
392 // prettify the date if we can, but we
393 // display as-is if we cannot or if
394 // it is invalid.
395 // So do the same here.
396
397 $value = $formatted;
398 }
399 }
400 }
401
402 return [
403 'frameCount' => $frameCount,
404 'loopCount' => $loopCount,
405 'duration' => $duration,
406 'text' => $text,
407 'bitDepth' => $bitDepth,
408 'colorType' => $colorType,
409 ];
410 }
411
420 private static function read( $fh, $size ) {
421 if ( $size > self::MAX_CHUNK_SIZE ) {
422 throw new Exception( __METHOD__ . ': Chunk size of ' . $size .
423 ' too big. Max size is: ' . self::MAX_CHUNK_SIZE );
424 }
425
426 return fread( $fh, $size );
427 }
428}
wfDebug( $text, $dest='all', array $context=[])
Sends a line to the debug log if enabled or, optionally, to a comment in output.
wfTimestamp( $outputtype=TS_UNIX, $ts=0)
Get a timestamp string in one of various formats.
static read( $fh, $size)
Read a chunk, checking to make sure its not too big.
static getMetadata( $filename)
$content
Definition router.php:78