JPEG comments

[Alex Tweedly]

Ken Ray wrote:

>On 9/27/05 10:13 AM, "Chris Carroll-Davis" <chris at eurotalk.co.uk> wrote:
>
>  
>
>>does anyone know of a way to write jpeg comments to an existing
>>file?  I think these are similar to the EXIF data written to files by
>>digital cameras.  I am working on MAc OS X.  "Preview" can read and
>>write these keywords - but it isn't scriptable!
>>    
>>
>
>Alex Tweedly announced some time back that he had a libEXIF for working with
>EXIF data... Alex, any update on this ?
>
>  
>
No, not really. It works well for reading EXIF data, but I never did do 
the other (harder) part, i.e. writing EXIF data. (I also didn't do any 
further Manufacturer-specific Makernote info extraction).

I found that the pure Transcript code was rather slow (*) (and the app I 
had in mind needed to be able to process fairly large numbers of photos) 
- so I basically put that project on the shelf until there is some 
mechanism for accessing binary data more quickly - whether numbered 
(fixed index) arrays or something else. For my project, I used an 
external tool (the command line version of Exiv2 from 
http://home.arcor.de/ahuggel/exiv2/index.html - available for Mac OSX 
and Linux as well as Windows, and free).

The Transcript library is available from revonline under username 
alextweedly called libEXIF

(*) I think I could handle 3-10 photos per second with libEXIF, and 
50-100 per second with exiv2.

-- 
Alex Tweedly       http://www.tweedly.net

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