Extracting EXIF data from images

EXIF is short for "Exchangeable Image File", a format that is a standard for storing interchange information in .JPG, .TIF, or .WAV files. Almost all new digital cameras use the EXIF annotation, storing information on the image such as shutter speed, exposure compensation, resolution, GPS information, and many other, as well user comments (used as image caption text).

EXIF metadata is a set of tag-value pairs, and most interesting tag here is the UserComment tag (field 0x9286 of the ExifIFD tag group).

There are many tools to extract this information from images, like perl exiftool, but the simplest is to use build-in functions as PHP's exif_read_data().

Links

• http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/EXIF.html
• https://en.wikipedia.org/wiki/Exchangeable_image_file_format
• https://productforums.google.com/forum/#!topic/picasa/FLMMYKioDrU
• http://php.net/manual/en/function.exif-read-data.php