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From Stephen Nesbitt <>
Subject Re: [Sanselan] - Help Parsing EXIF Info embedded in PNG
Date Thu, 04 Mar 2010 02:49:16 GMT
Hi Matthew:

On Wednesday 03 March 2010 06:35:38 pm Charles Matthew Chen wrote:
>    First, calling getText() on Sanselan's zTXt chunk returns the
> uncompressed contents:
Good - that is very nice to know. Am I correct in assuming that the text 
returned is a set of hex values?

>    Next, I'm not sure exactly what is meant by "raw" Exif data, but
> Exif is a binary format.  It'd be strange to store it in a zTXt chunk.
Strange or not - that's what I think is happening. 

The application that created the PNG is digikam and was the result of 
digikam's convert from jpeg to png tool/capability. What I suspect is 
happening is that digikam is taking the binary EXIF data and storing it in a 
PNG zTXt chunk with a keyword of "Raw profile type"

>    Phil's exiftool documentation is in many ways the defacto standard
> for image metadata practices, especially for these non-standardized
> dark corners.  In the absence of a standard, I'm not sure what you're
> looking for or asking to be implemented.
Essentially I need a Java version of exiftool's capability to extract EXIF 
info from a PNG. I am not sure that such a capability really falls within 
Sanselan's responsibility.

Knowing that Sanselan is deflating the zTXt chunk as part of the getText() 
method is very useful and helps illuminate the dark corners. It might be nice 
to add a note to the Java doc to that point.

Thanks for the info!


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