[jira] [Commented] (DAFFODIL-1742) TIFF - need DFDL schema and approach to TIFF

["Michael Beckerle (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DAFFODIL-1742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16661408#comment-16661408 ] 

Michael Beckerle commented on DAFFODIL-1742:
--------------------------------------------

This is a major feature requirement for DFDL v2.0 - TIFF is base+offset oriented. The format can't be parsed end to end. Each record gives an offset from the end of a header, to the next record, so they can, literally, be backwards in the file - one must "seek" to parse this.

It is important that any approach to this is (a) declarative (b) invertible - unparsing should also work - resulting in each record following the previous one, but these offsets from the base have to get computed automatically much the way stored lengths do (via outputValueCalc). 

> TIFF - need DFDL schema and approach to TIFF
> --------------------------------------------
>
>                 Key: DAFFODIL-1742
>                 URL: https://issues.apache.org/jira/browse/DAFFODIL-1742
>             Project: Daffodil
>          Issue Type: New Feature
>          Components: DFDL Language, DFDL Schemas
>            Reporter: Michael Beckerle
>            Priority: Minor
>
> TIFF image format is not something DFDL v1.0 can describe.
> Nevertheless we need an approach that illustrates how to deal with it.
> I *think* this means a preprocessing program, and then a DFDL schema to turn the result of the preprocessor into an Infoset.  For unparsing, a post-processor also.
> The right approach remains to be seen, but we need to show how to deal with TIFF.



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