Add these functions to a class, then just call $class::getImageDpi($filename) to get the DPI returned. DPI is searched both in the image header-data and the EXIF data. Use these functions according to MIT license.
[code lang=”php”]
/**
* @param string $filename
* @return array
* @throws Exception
*/
public static function getImageDpi($filename)
{
if (!empty($filename)
&& file_exists($filename)
) {
$fileMime = self::getFileMimeType($filename);
if ($fileMime == ‘image/jpeg; charset=binary’
|| $fileMime == ‘image/jpg; charset=binary’
|| $fileMime == ‘image/jpeg2; charset=binary’
) {
return self::getImageJpgDpi($filename);
} else if ($fileMime == ‘image/png; charset=binary’) {
return self::getImagePngDpi($filename);
} else {
return array(
‘x’ => 72,
‘y’ => 72,
);
}
} else {
Throw new \Exception(‘Invalid parameters’);
}
}
/**
* Uses unix command file -bi for determining file typ.
*
* jpeg = image/jpeg; charset=binary
* gif = image/gif; charset=binary
* pdf = application/pdf; charset=binary
*
* @static
* @param string $absolutePath
* @throws Exception
* @return string|bool
*/
public static function getFileMimeType($absolutePath)
{
if (!empty($absolutePath)) {
if (file_exists($absolutePath)) {
if ($return = exec(
‘file -bi — ‘ . escapeshellarg($absolutePath))
) {
return $return;
}
}
} else {
Throw new Exception(
‘Invalid parameters for ‘ . __FUNCTION__
. ‘ in ‘ . __FILE__);
}
return false;
}
/**
* @param string $filename
* @return array
* @throws Exception
*/
public static function getImageJpgDpi($filename)
{
if (!empty($filename)
&& file_exists($filename)
) {
$dpi = 0;
$fp = @fopen($filename, ‘rb’);
if ($fp) {
if (fseek($fp, 6) == 0)
{
if (($bytes = fread($fp, 16)) !== false)
{
if (substr($bytes, 0, 4) == “JFIF”)
{
$JFIF_density_unit = ord($bytes[7]);
$JFIF_X_density = ord($bytes[8])*256 + ord($bytes[9]);
$JFIF_Y_density = ord($bytes[10])*256 + ord($bytes[11]);
if ($JFIF_X_density == $JFIF_Y_density)
{
if ($JFIF_density_unit == 1) {
$dpi = $JFIF_X_density;
} else if ($JFIF_density_unit == 2) {
$dpi = $JFIF_X_density * 2.54;
}
}
}
}
}
fclose($fp);
}
if (empty($dpi)) {
if ($exifDpi = self::getImageDpiFromExif($filename)) {
$dpi = $exifDpi;
}
}
if (!empty($dpi)) {
return array(
‘x’ => $dpi,
‘y’ => $dpi,
);
} else {
return array(
‘x’ => 72,
‘y’ => 72,
);
}
} else {
Throw new \Exception(‘Invalid parameters’);
}
}
/**
* @static
* @param string $filename
* @return array
* @throws Exception
*/
public static function getImagePngDpi($filename)
{
if (!empty($filename)
&& file_exists($filename)
) {
$fh = fopen($filename, ‘rb’);
if (!$fh) {
return false;
}
$buf = array();
$x = 0;
$y = 0;
$units = 0;
while(!feof($fh))
{
array_push($buf, ord(fread($fh, 1)));
if (count($buf) > 13)
array_shift($buf);
if (count($buf) < 13)
continue;
if ($buf[0] == ord('p') &&
$buf[1] == ord('H') &&
$buf[2] == ord('Y') &&
$buf[3] == ord('s'))
{
$x = ($buf[4] << 24) + ($buf[5] << 16) + ($buf[6] << 8) + $buf[7];
$y = ($buf[8] << 24) + ($buf[9] << 16) + ($buf[10] << 8) + $buf[11];
$units = $buf[12];
break;
}
}
fclose($fh);
if ($x != false
&& $units == 1
) {
$x = round($x * 0.0254);
}
if ($y != false
&& $units == 1
) {
$y = round($y * 0.0254);
}
if (empty($x)
&& empty($y)
) {
if ($exifDpi = self::getImageDpiFromExif($filename)) {
$x = $exifDpi;
$y = $exifDpi;
}
}
if (!empty($x)
|| !empty($y)
) {
return array(
'x' => $x,
‘y’ => $y,
);
} else {
return array(
‘x’ => 72,
‘y’ => 72,
);
}
} else {
Throw new \Exception(‘Invalid parameters’);
}
}
/**
* Read EXIF data.
*
* @static
* @param string $filename
* @throws \Exception
* @return bool|float
*/
public static function getImageDpiFromExif($filename)
{
if (!empty($filename)
&& file_exists($filename)
) {
if (function_exists(‘exif_read_data’)) {
if ($exifData = exif_read_data($filename)) {
if (isset($exifData[‘XResolution’])) {
if (strpos($exifData[‘XResolution’], ‘/’) !== false) {
if ($explode = explode(‘/’, $exifData[‘XResolution’])) {
return (float) ((int) $explode[0] / (int) $explode[1]);
}
} else {
return (int) $exifData[‘XResolution’];
}
} else if (isset($exifData[‘YResolution’])) {
if (strpos($exifData[‘YResolution’], ‘/’) !== false) {
if ($explode = explode(‘/’, $exifData[‘YResolution’])) {
return (float) ((int) $explode[0] / (int) $explode[1]);
}
} else {
return (int) $exifData[‘YResolution’];
}
}
}
} else {
Throw new \Exception(‘Incompatible system.’);
}
} else {
Throw new \Exception(‘Invalid parameters.’);
}
return false;
}
[/code]