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Re: EXIF tag handling in Java

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Thanks to all of you who have responded. I should have enough information 
now to be able to dig into the issue of adding comments to images in the 
form of EXIF tags. 

Perhaps I should explain what I'm doing. I have a Java program, run 
overnight as a cron job, that can walk a directory tree and decorate it 
with a thumbnail of every new or modified image it finds. As I run an in-
house webserver, this is enough to let a PHP script generate on-the-fly 
menus from directories in the tree which contain clickable links to all 
files in the directory. Links to images display the thumbnail as part of 
that menu entry. However, this doesn't work if you simply point a browser 
at a local copy of the directory structure, so the Java program can also 
generate a linked set of static menus that work in the same way for 
people who don't run a web server. 

This is working reliably and well. It has met my design target of 
automatically indexing sets of images as they are dropped on a hard drive
so they can be scrolled through using smaller images that those can be 
selected so the full resolution image can be seen.

Now I'd like to display descriptions, when they are available,  under the 
thumbnails.

Thanks to all of you I now know that I can write a program to add the 
descriptions to the images as EXIF 'Comment' tags and in parallel I've 
checked that PHP can extract the content of those tags in order to add 
them to the on-the-fly menus and that Java can do the same for the static 
menus.

The only issue is speed: the PHP library routines to check that the image 
is the right type to have EXIF tags and to extract the tags require each 
image to be read several times: (1) to display the thumbnail, (2) to see 
if it is the right type to hold tags [this can probably be skipped] and 
(3) to extract the Comment tag's content. Currently only (1) happens, so 
I need to benchmark things to see if the PHP script is fast enough to 
support extracting captions from EXIF tags: this is not a consideration 
for the Java menu builder since this is never run when a user wants to 
see an list of images *right now*. 

If the PHP menu generator is unacceptably slow when dealing with EXIF 
tags, I'll use the aesthetically ugly trick of keeping the captions as a 
separate CSV list (filename,caption) which will probably be faster since 
at the start of the run it can be loaded into a Hashtable (Java) or 
associative array (PHP) once and will stay in memory while the menu 
builder is running.

Thanks again for your help.


-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

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Thread

EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-24 21:37 +0000
  Re: EXIF tag handling in Java Marty Blake <blake3334@nowhere.invalid> - 2012-03-24 23:13 -0400
    Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 13:09 +0000
      Re: EXIF tag handling in Java Jeff Higgins <jeff@invalid.invalid> - 2012-03-25 11:42 -0400
        Re: EXIF tag handling in Java Jeff Higgins <jeff@invalid.invalid> - 2012-03-25 12:22 -0400
          Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 17:10 +0000
        Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 16:46 +0000
          Re: EXIF tag handling in Java Jeff Higgins <jeff@invalid.invalid> - 2012-03-25 12:59 -0400
            Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 17:15 +0000
              Re: EXIF tag handling in Java Jeff Higgins <jeff@invalid.invalid> - 2012-03-25 14:08 -0400
                Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 18:34 +0000
  Re: EXIF tag handling in Java Knute Johnson <nospam@knutejohnson.com> - 2012-03-25 10:46 -0700
    Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 18:13 +0000
  Re: EXIF tag handling in Java "John B. Matthews" <nospam@nospam.invalid> - 2012-03-25 14:45 -0400
    Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-25 23:37 +0000
      Re: EXIF tag handling in Java Lew <lewbloch@gmail.com> - 2012-03-26 11:56 -0700
        Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-26 19:48 +0000
        Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-26 19:52 +0000
          Re: EXIF tag handling in Java Lew <lewbloch@gmail.com> - 2012-03-26 13:29 -0700
            Re: EXIF tag handling in Java Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-26 21:58 +0000
              Re: EXIF tag handling in Java Lew <lewbloch@gmail.com> - 2012-03-26 16:24 -0700
                Re: EXIF tag handling in Java Gene Wirchenko <genew@ocis.net> - 2012-03-26 18:19 -0700
                Re: EXIF tag handling in Java Lew <lewbloch@gmail.com> - 2012-03-26 19:03 -0700
                Re: EXIF tag handling in Java Gene Wirchenko <genew@ocis.net> - 2012-03-27 09:06 -0700

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