[Spike] Investigate meta data extracting

[lenaorobei]

As a Merchant I want Magento Media Storage to parse image meta data that is available in the file and expose it on image details page so that I can manage it and use for filtering images

Additional context
#1183

Open questions:

• is there any required set of fields that exist in image meta data? Like title, description, keywords. Or any fields can be removed/added to the file according to standard?
• is there a way in a meta data file to define what fields can be edited by user in the application? e.g. Camera data, image format, creation and modification date can not be edited

[sivaschenko]

Neet to try exif_read_data on different image formats

[sivaschenko]

We can use the APP13 IPTC data of the image for reading and saving metadata.

Reading the metadata:

$iptcHeaders = [
    'title' => '2#005',
    'headline' => '2#105',
    'keywords' => '2#025'
];

getimagesize('image.jpg', $info);
$decodedMetadata = iptcparse($info['APP13']);
$keywords = $decodedMetadata[$iptcHeaders['keywords']];
$title = $decodedMetadata[$iptcHeaders['headline']];

Saving the metadata:

$newTitle = 'New Title';
$length = strlen($newTitle);
$retval = chr(0x1C) . chr(2) . chr(substr($iptcHeaders['headline'], 2));
if($length < 0x8000) {
    $retval .= chr($length >> 8) .  chr($length & 0xFF);
} else {
    $retval .= chr(0x80) .
        chr(0x04) .
        chr(($length >> 24) & 0xFF) .
        chr(($length >> 16) & 0xFF) .
        chr(($length >> 8) & 0xFF) .
        chr($length & 0xFF);
}
$data = $retval . $newTitle;

$content = iptcembed($data, $filename);

$file = fopen($filename, "wb");
fwrite($file, $content);
fclose($file);

IPTC standard: https://www.iptc.org/std/photometadata/specification/IPTC-PhotoMetadata