<?php
/**
* fast-image-size image type jpeg
* @package fast-image-size
* @copyright (c) Marc Alexander <admin@m-a-styles.de>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace FastImageSize\Type;
class TypeJpeg extends TypeBase
{
/** @var int JPEG max header size. Headers can be bigger, but we'll abort
* going through the header after this */
const JPEG_MAX_HEADER_SIZE = 786432; // = 768 kiB
/** @var string JPEG header */
const JPEG_HEADER = "\xFF\xD8";
/** @var string Start of frame marker */
const SOF_START_MARKER = "\xFF";
/** @var string End of image (EOI) marker */
const JPEG_EOI_MARKER = "\xD9";
/** @var array JPEG SOF markers */
protected $sofMarkers = array(
"\xC0",
"\xC1",
"\xC2",
"\xC3",
"\xC5",
"\xC6",
"\xC7",
"\xC9",
"\xCA",
"\xCB",
"\xCD",
"\xCE",
"\xCF"
);
/** @var string|bool JPEG data stream */
protected $data = '';
/** @var int Data length */
protected $dataLength = 0;
/**
* {@inheritdoc}
*/
public function getSize($filename)
{
// Do not force the data length
$this->data = $this->fastImageSize->getImage($filename, 0, self::JPEG_MAX_HEADER_SIZE, false);
// Check if file is jpeg
if ($this->data === false || substr($this->data, 0, self::SHORT_SIZE) !== self::JPEG_HEADER)
{
return;
}
// Look through file for SOF marker
$size = $this->getSizeInfo();
$this->fastImageSize->setSize($size);
$this->fastImageSize->setImageType(IMAGETYPE_JPEG);
}
/**
* Get size info from image data
*
* @return array An array with the image's size info or an empty array if
* size info couldn't be found
*/
protected function getSizeInfo()
{
$size = array();
// since we check $i + 1 we need to stop one step earlier
$this->dataLength = strlen($this->data) - 1;
$sofStartRead = true;
// Look through file for SOF marker
for ($i = 2; $i < $this->dataLength; $i++)
{
$marker = $this->getNextMarker($i, $sofStartRead);
if (in_array($marker, $this->sofMarkers))
{
// Extract size info from SOF marker
return $this->extractSizeInfo($i);
}
else
{
// Extract length only
$markerLength = $this->extractMarkerLength($i);
if ($markerLength < 2)
{
return $size;
}
$i += $markerLength - 1;
continue;
}
}
return $size;
}
/**
* Extract marker length from data
*
* @param int $i Current index
* @return int Length of current marker
*/
protected function extractMarkerLength($i)
{
// Extract length only
list(, $unpacked) = unpack("H*", substr($this->data, $i, self::LONG_SIZE));
// Get width and height from unpacked size info
$markerLength = hexdec(substr($unpacked, 0, 4));
return $markerLength;
}
/**
* Extract size info from data
*
* @param int $i Current index
* @return array Size info of current marker
*/
protected function extractSizeInfo($i)
{
// Extract size info from SOF marker
list(, $unpacked) = unpack("H*", substr($this->data, $i - 1 + self::LONG_SIZE, self::LONG_SIZE));
// Get width and height from unpacked size info
$size = array(
'width' => hexdec(substr($unpacked, 4, 4)),
'height' => hexdec(substr($unpacked, 0, 4)),
);
return $size;
}
/**
* Get next JPEG marker in file
*
* @param int $i Current index
* @param bool $sofStartRead Flag whether SOF start padding was already read
*
* @return string Next JPEG marker in file
*/
protected function getNextMarker(&$i, &$sofStartRead)
{
$this->skipStartPadding($i, $sofStartRead);
do {
if ($i >= $this->dataLength)
{
return self::JPEG_EOI_MARKER;
}
$marker = $this->data[$i];
$i++;
} while ($marker == self::SOF_START_MARKER);
return $marker;
}
/**
* Skip over any possible padding until we reach a byte without SOF start
* marker. Extraneous bytes might need to require proper treating.
*
* @param int $i Current index
* @param bool $sofStartRead Flag whether SOF start padding was already read
*/
protected function skipStartPadding(&$i, &$sofStartRead)
{
if (!$sofStartRead)
{
while ($this->data[$i] !== self::SOF_START_MARKER)
{
$i++;
}
}
}
}