I came here looking for something similar to the getJPEGresolution function, but noticed the drawbacks that were pointed out in the last post. So, after drawing on some other code examples on the web, I put together the following function which should always properly return the correct values. (But remember that you still need to have the EXIF extension installed with your instance of PHP for this to work!)
<?php
function jpeg_dpi($filename)
{
if ( exif_imagetype($filename) != IMAGETYPE_JPEG ) {
return false;
} else {
$exif = exif_read_data($filename, 'IFD0');
}
$x = $y = 0;
if ( isset($exif['XResolution']) && isset($exif['YResolution']) ) {
$x = intval(preg_replace('@^(\\d+)/(\\d+)$@e', '$1/$2', $exif['XResolution']));
$y = intval(preg_replace('@^(\\d+)/(\\d+)$@e', '$1/$2', $exif['YResolution']));
}
if ( !$x && !$y && $fp = fopen($filename, 'r') ) {
$string = fread($fp, 20);
fclose($fp);
$data = bin2hex(substr($string, 14, 4));
$x = hexdec(substr($data, 0, 4));
$y = hexdec(substr($data, 4, 4));
}
if ( $x || $y ) {
return array($x, $y);
}
return false;
}
?>
This function returns an array with the x-resolution, y-resolution when they can be determined, otherwise FALSE.
