If
you have a digital camera, you probably also have a digital
photo gallery of memorable moments. And if you have a digital photo
gallery, you’re almost sure to have run into a very common problem: organizing
your photos so that they can be easily searched and indexed.

Now,
you might not know this, but most digital cameras automatically embed
descriptive metadata in the headers of the images they create. These headers,
called EXchangeable Image File
(EXIF) headers, contain information on the camera make and model, the time and
date the photo was taken, the technical specifications of the photo (shutter
speed, aperture and so on) and a thumbnail of the image. Additionally, many
image editors allow you to supplement these automatically generated headers
with descriptive text of your own – for example, “Sally’s first football
game” or “Getting drunk in Malta”.

I’m
sure you can see where I’m going with this. With a little bit of imagination
and creative thinking, it’s possible to use the headers generated by your
camera (and, if you have the time and motivation, further supplemented by you)
to automatically organize and describe your photo collection. This article will
show you how, using PHP‘s
EXIF functions.

Step 1: Make sure your PHP build supports EXIF

In
order to read EXIF headers, your PHP build must include support for the EXIF
module. You can check whether this support is enabled, by creating a PHP script
containing the code shown in Listing A.

Listing A

<?php
phpinfo();
?>

View
the output of this script in your Web browser, and review the list of
extensions to see if EXIF is included. If it is, move to the next step. If not,
you’ll need to activate PHP’s EXIF functions, either
by un-commenting the extension line in php.ini (Windows) or
recompiling your PHP build with the –enable-exif argument (UNIX). More information on how to do this is
available at the PHP Web site.

Step 2: Move your photos into a single directory

Next,
collect all your photos into a single directory under the Web server document
root. This is also a good time to add your own descriptive comments to each
image (although this is not essential). A number of good shareware and freeware
tools are available to help you do this; take a look at Exifer for Windows or RoboPhoto.

Step 3: Write code to read photo headers and comments

The
final step is to write the PHP scripts that will extract EXIF data from your
images and automatically generate a Web page with thumbnails, technical
information and links to larger versions of each image. There are two scripts
here: the first one, gallery.php, (See Listing B) looks for photos and extracts EXIF headers from them,
while the second one, thumbnail.php, (See Listing C) is responsible for extracting the thumbnail image from
each photo.

Listing B – Here’s the code for gallery.php

<html>
<head></head>
<body>
<table>
<?php
// define directory path
$dir = “.”;

// iterate through files
// look for JPEGs
if (is_dir($dir)) {
    if ($dh = opendir($dir)) {
        while (($file = readdir($dh)) !== false) {
            if (preg_match(“/.jpg/”, $file)) {
                // read EXIF headers
                $exif = exif_read_data($file, 0, true);
                echo “<tr>”;
                // get thumbnail
                // link to full image
                echo “<td valign=top><a href=$dir/$file><imgsrc=thumbnail.php?file=$file></a><td>”;
                echo “<td valign=top><font size=-1>”;
                // get file name
                echo “File: <b>” . $exif[‘FILE’][‘FileName’] . “</b><br/>”;
                // get timestamp
                echo “Timestamp: ”  . $exif[‘IFD0’][‘DateTime’] . “<br/>”;
                // get image dimensions
                echo “Dimensions: ” . $exif[‘COMPUTED’][‘Height’] . ” x ” . $exif[‘COMPUTED’][‘Height’] . ” <br/>”;
                // get camera make and model
                echo “Camera: ” . $exif[‘IFD0’][‘Model’];
                echo “</font></td>”;
                echo “</tr>”;
           }
        }
       closedir($dh);
   }
}
?>
</table>
</body>
</html>

This
script uses PHP’s directory functions to retrieve a
list of all the JPEG images in the directory, and then uses the exif_read_data() function to read the EXIF headers from each image as an
array. Each image is displayed as a thumbnail using information provided by thumbnail.php, and each
thumbnail is itself hyperlinked to its parent image. Relevant information—image
name, dimensions, timestamp and camera model—is extracted from these headers
and displayed with each thumbnail.

If
you used an EXIF editor to add your own comments to the images, you can access
the appropriate array elements to retrieve and display that information as
well. Look inside the $exif array with print_r($exif) to find out
the array path for your custom metadata.

Note:
Different camera manufacturers use the EXIF headers in different ways. If the
output of the script above appears to be missing some information, you should
look inside the $exif array with print_r($exif) to find out
exactly how your camera writes the EXIF data, and make appropriate adjustments
to the array keys in the script above (Listing
B).

Listing C – And here’s the code for thumbnail.php

<?php
// define directory path
$dir = “.”;
$image = exif_thumbnail($dir . “/” . $_GET[‘file’]);
header(“Content-Type: image/jpeg”);
echo $image;
?>

This
script is very simple—it retrieves the image file name from the URL and uses
the exif_thumbnail() function to
extract a thumbnail from the named image. This thumbnail is then sent to the
browser, together with an appropriate header, for display.

Place
both these scripts in the directory containing your photos, and then use your
Web browser to access gallery.php. You should see thumbnails of
the images in the directory, together with descriptive information on each.
Clicking a thumbnail should take you to the larger parent image.

Figure A is an example
screenshot of what the output might look like:

Figure A
An example screenshot

And
there you have it—an automatically generated photo gallery! As you copy new
images to the folder, they will automatically show up in the gallery listing.
Isn’t that neat?

Note: You can
place the scripts created in Step 3
in a different directory from the one containing your photos, so long as you
remember to update the $dir
variable at the top of each script with the correct path to the photo
collection.