Exif data is actually an extension of the TIFF file format. TIFF
images consist of a number of {@link PelIfd Image File Directories}
(IFDs), each containing a number of {@link PelEntry entries}. The
IFDs are linked to each other --- one can get hold of the first one
with the {@link getIfd()} method.
To parse a TIFF image for Exif data one would do:
$tiff = new PelTiff($data);
$ifd0 = $tiff->getIfd();
$exif = $ifd0->getSubIfd(PelIfd::EXIF);
$ifd1 = $ifd0->getNextIfd();
Should one have some image data of an unknown type, then the {@link PelTiff::isValid()} function is handy: it will quickly test if the
data could be valid TIFF data. The {@link PelJpeg::isValid()}
function does the same for JPEG images.
$exif->setTiff($tiff);
} else {
/*
* Surprice, surprice: Exif data is really just TIFF data! So we
* extract the PelTiff object for later use.
*/
println('Found existing APP1 section.');
$tiff = $exif->getTiff();
}
} elseif (PelTiff::isValid($data)) {
/*
* The data was recognized as TIFF data. We prepare a PelTiff
* object to hold it, and record in $file that the PelTiff object is
* the top-most object (the one on which we will call getBytes).
*/
$tiff = $file = new PelTiff();
/* Now load the data. */
$tiff->load($data);
} else {
/*
* The data was not recognized as either JPEG or TIFF data.
* Complain loudly, dump the first 16 bytes, and exit.
*/
println('Unrecognized image format! The first 16 bytes follow:');
PelConvert::bytesToDump($data->getBytes(0, 16));
exit(1);
}
/*
* TIFF data has a tree structure much like a file system. There is a
* root IFD (Image File Directory) which contains a number of entries
* and maybe a link to the next IFD. The IFDs are chained together
}
/*
* We typically need lots of RAM to parse TIFF images since they tend
* to be big and uncompressed.
*/
ini_set('memory_limit', '32M');
foreach ($argv as $file) {
println('Reading file "%s".', $file);
$data = new PelDataWindow(file_get_contents($file));
if (PelJpeg::isValid($data)) {
$jpeg = new PelJpeg();
$jpeg->load($data);
$app1 = $jpeg->getExif();
$tiff = $app1->getTiff();
} elseif (PelTiff::isValid($data)) {
$tiff = new PelTiff($data);
} else {
println('Unrecognized image format! Skipping.');
continue;
}
$ifd0 = $tiff->getIfd();
$entry = $ifd0->getEntry(PelTag::DATE_TIME);
if ($entry == null) {
println('Skipping %s because no DATE_TIME tag was found.', $file);
continue;
}
$time = $entry->getValue();
do {
$new = gmdate('Y:m:d-H:i:s', $time) . strchr($file, '.');
println('Trying file name %s', $new);
$time++;
exit(1);
}
if (!is_readable($file)) {
printf("Unable to read %s!\n", $file);
exit(1);
}
/*
* We typically need lots of RAM to parse TIFF images since they tend
* to be big and uncompressed.
*/
ini_set('memory_limit', '32M');
$data = new PelDataWindow(file_get_contents($file));
if (PelJpeg::isValid($data)) {
$img = new PelJpeg();
} elseif (PelTiff::isValid($data)) {
$img = new PelTiff();
} else {
print "Unrecognized image format! The first 16 bytes follow:\n";
PelConvert::bytesToDump($data->getBytes(0, 16));
exit(1);
}
/* Try loading the data. */
$img->load($data);
print $img;
/* Deal with any exceptions: */
if (count(Pel::getExceptions()) > 0) {
print "\nThe following errors were encountered while loading the image:\n";
foreach (Pel::getExceptions() as $e) {
print "\n" . $e->__toString();
}
}