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TypeJpeg.php
001 <?php
002
003 /**
004 * fast-image-size image type jpeg
005 * @package fast-image-size
006 * @copyright (c) Marc Alexander <admin@m-a-styles.de>
007 *
008 * For the full copyright and license information, please view the LICENSE
009 * file that was distributed with this source code.
010 */
011
012 namespace FastImageSize\Type;
013
014 class TypeJpeg extends TypeBase
015 {
016 /** @var int JPEG max header size. Headers can be bigger, but we'll abort
017 * going through the header after this */
018 const JPEG_MAX_HEADER_SIZE = 786432; // = 768 kiB
019
020 /** @var string JPEG header */
021 const JPEG_HEADER = "\xFF\xD8";
022
023 /** @var string Start of frame marker */
024 const SOF_START_MARKER = "\xFF";
025
026 /** @var string End of image (EOI) marker */
027 const JPEG_EOI_MARKER = "\xD9";
028
029 /** @var array JPEG SOF markers */
030 protected $sofMarkers = array(
031 "\xC0",
032 "\xC1",
033 "\xC2",
034 "\xC3",
035 "\xC5",
036 "\xC6",
037 "\xC7",
038 "\xC9",
039 "\xCA",
040 "\xCB",
041 "\xCD",
042 "\xCE",
043 "\xCF"
044 );
045
046 /** @var string|bool JPEG data stream */
047 protected $data = '';
048
049 /** @var int Data length */
050 protected $dataLength = 0;
051
052 /**
053 * {@inheritdoc}
054 */
055 public function getSize($filename)
056 {
057 // Do not force the data length
058 $this->data = $this->fastImageSize->getImage($filename, 0, self::JPEG_MAX_HEADER_SIZE, false);
059
060 // Check if file is jpeg
061 if ($this->data === false || substr($this->data, 0, self::SHORT_SIZE) !== self::JPEG_HEADER)
062 {
063 return;
064 }
065
066 // Look through file for SOF marker
067 $size = $this->getSizeInfo();
068
069 $this->fastImageSize->setSize($size);
070 $this->fastImageSize->setImageType(IMAGETYPE_JPEG);
071 }
072
073 /**
074 * Get size info from image data
075 *
076 * @return array An array with the image's size info or an empty array if
077 * size info couldn't be found
078 */
079 protected function getSizeInfo()
080 {
081 $size = array();
082 // since we check $i + 1 we need to stop one step earlier
083 $this->dataLength = strlen($this->data) - 1;
084
085 $sofStartRead = true;
086
087 // Look through file for SOF marker
088 for ($i = 2; $i < $this->dataLength; $i++)
089 {
090 $marker = $this->getNextMarker($i, $sofStartRead);
091
092 if (in_array($marker, $this->sofMarkers))
093 {
094 // Extract size info from SOF marker
095 return $this->extractSizeInfo($i);
096 }
097 else
098 {
099 // Extract length only
100 $markerLength = $this->extractMarkerLength($i);
101
102 if ($markerLength < 2)
103 {
104 return $size;
105 }
106
107 $i += $markerLength - 1;
108 continue;
109 }
110 }
111
112 return $size;
113 }
114
115 /**
116 * Extract marker length from data
117 *
118 * @param int $i Current index
119 * @return int Length of current marker
120 */
121 protected function extractMarkerLength($i)
122 {
123 // Extract length only
124 list(, $unpacked) = unpack("H*", substr($this->data, $i, self::LONG_SIZE));
125
126 // Get width and height from unpacked size info
127 $markerLength = hexdec(substr($unpacked, 0, 4));
128
129 return $markerLength;
130 }
131
132 /**
133 * Extract size info from data
134 *
135 * @param int $i Current index
136 * @return array Size info of current marker
137 */
138 protected function extractSizeInfo($i)
139 {
140 // Extract size info from SOF marker
141 list(, $unpacked) = unpack("H*", substr($this->data, $i - 1 + self::LONG_SIZE, self::LONG_SIZE));
142
143 // Get width and height from unpacked size info
144 $size = array(
145 'width' => hexdec(substr($unpacked, 4, 4)),
146 'height' => hexdec(substr($unpacked, 0, 4)),
147 );
148
149 return $size;
150 }
151
152 /**
153 * Get next JPEG marker in file
154 *
155 * @param int $i Current index
156 * @param bool $sofStartRead Flag whether SOF start padding was already read
157 *
158 * @return string Next JPEG marker in file
159 */
160 protected function getNextMarker(&$i, &$sofStartRead)
161 {
162 $this->skipStartPadding($i, $sofStartRead);
163
164 do {
165 if ($i >= $this->dataLength)
166 {
167 return self::JPEG_EOI_MARKER;
168 }
169 $marker = $this->data[$i];
170 $i++;
171 } while ($marker == self::SOF_START_MARKER);
172
173 return $marker;
174 }
175
176 /**
177 * Skip over any possible padding until we reach a byte without SOF start
178 * marker. Extraneous bytes might need to require proper treating.
179 *
180 * @param int $i Current index
181 * @param bool $sofStartRead Flag whether SOF start padding was already read
182 */
183 protected function skipStartPadding(&$i, &$sofStartRead)
184 {
185 if (!$sofStartRead)
186 {
187 while ($this->data[$i] !== self::SOF_START_MARKER)
188 {
189 $i++;
190 }
191 }
192 }
193 }
194