The IT Blog

Tag: Sanselan

  • Sanselan und Vendor Notes

    Metadaten in Bildern sind in Java scheinbar echt gar nicht so einfach.  In einem früheren Artikel habe ich kurz aufgelistet, welche Metadata-Libraries ich immerhin schon mal ausgemacht habe. – Sanselan sah da ja schon gar nicht schlecht aus.

    Bei einem ersten Test bin ich dann aber darauf gestoßen, dass scheinbar die Vendor Notes echte Probleme bereiten können. Ich wollte eigentlich nur die Exif-Daten auslesen und in eine andere Datei kopieren. Die eigentlichen Exif-Daten waren alle super. Die Vendor-Notes meiner Sony Alpha 350 sahen auch ganz gut aus (keine genauen Vergleiche) – ein Bild einer Canon Powershot A570 IS war schon anspruchsvoller. Ca. die Hälfte der Vendor-Notes waren verändert bis unbrauchbar 🙁

    Brav wie ich bin, erst mal auf der Mailingliste nachgefragt… keine Antwort – hm. Also mal brav einen Bug eröffnet. Und danach gesehen, dass das Verhalten in der Doku quasi schon angekündigt ist:

    Note that this uses the “Lossless” approach – in order to preserve data embedded in the EXIF segment that it can’t parse (such as Maker Notes), this algorithm avoids overwriting any part of the original segment that it couldn’t parse. This can cause the EXIF segment to grow with each update, which is a serious issue, since all EXIF data must fit in a single APP1 segment of the Jpeg image.
    http://commons.apache.org/sanselan/api-release/org/apache/sanselan/formats/jpeg/exifRewrite/ExifRewriter.html

    Tjo. Blöd. Klar Blöd auch von den Kameraherstellern, dass diese Einträge proprietär sind – aber noch dümmer, dass es unter Windows gefühlte 10.000 Programme gibt, die die Exif-Daten einfach ändern können und sich das mit Java langsam echt zu einem ernsthaften Problem auswächst.

    Als nächstes versuche ich jetzt Imagero, der ist zwar nicht frei, aber vielleicht geht’s da wenigstens.

  • Java Library for reading & writing EXIF, XMP and IPTC in JPEGs

    Finally it seems that I’ve found a pure Java Library that can read and write XMP Data to and from JPEGs!

    In the past time I’ve been googling for such a library repeatedly. There are quite some libraries for just reading EXIF or IPTC data. Amongst others are Drew Noakes’ library and Imagero. As I am on the verge of adding more metadata functionality to my self-made image database I had 2 issues:

    1. A decision of how to store labels and descriptions to images: a database only without touching the images or IPTC, XMP within images (with cached information to a database). Finally I decided that I wanted to use XMP(or IPTC so that the information is kept close to the image.
    2. A library for this!

    What I’ve found so far (incomplete listing as I came across QUITE some libs for reading data):

    Imagero and Drew Noakes: Until now I was using Drew Noakes library for reding EXIF data – which was absolutely okay but couldn’t write any data 🙁 Imagero supports writing of IPTC and XMP (from what I’ve read) and is even free for non-commercial usage. But it’s not true open source and you need to request a licence every year (which works w/out problems!). Judging the work Andrey Kusnetsov (maintainer of Imagero) is putting into it I think, that’s quite acceptable.

    Adobe XMP SDK: Adobe – as the inventor of XMP – has released an SDK for reading/writing XMP. Most of the SDK is written in C, the SDK Core is also available in Java (great!) but the functionality to get and write the XMP to and from files .. is not available as Java. Quite annoying.

    Apache Sanselan: When searching for Apache Sanselan you most likely end up at the incubator-site which says that the project is in the stat of migrating into apache – the mailinglist also doesn’t work. The simple reason: Sanselan is already a part of Apache Commons. So, this new link is the place to go. The most interesting thing of Sanselan is the format support:

    • JPEG IPTC support: read (yes), write (soon), Can read IPTC data from exsiting JPEG/JFIF files WITHOUT modifying image data.
    • JPEG EXIF: read (yes), write (yes), Can read and write EXIF data to and from exsiting JPEG/JFIF files WITHOUT modifying image data.
    • XMP: read (yes), write (yes), Can read XMP XML (as as String) from […] JPEG […]. Can remove, insert and update XMP XML into existing JPEG files.

    Update: the downside of Sanselan is that development seems to have stalled. The current release is 0.97 from February 14th, 2009. :-(((