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Date Posted: 06:05:33 01/13/04 Tue
Author: glup
Subject: Re: libtiff v3.6.x support; Custom Tags
In reply to: Michel 's message, "Re: libtiff v3.6.x support; Custom Tags" on 19:42:29 01/12/04 Mon

>Thanks for the info. It is definitely on the list.
>Before spring I intend to release version 2.5, and
>this could be in there.
Sounds nice to me!

3 major points for the wish-list regarding tiff:

1. Collection of Tiff Tags
Please include a list to read all existing tags, something like

TTiffTag = class(CollectionItem)
property Tag: word read ...;
property Type: word read ...;
property Length: longword read ...;
property Value: variant read ... write ...;
property IsRaw: boolean read ...;

TTiffTags = class(Collection)
property Count: integer read ...;
property Item[ const aIndex: integer ]: TTiffTag read ...; default;

function Add(const aTag: word;
const aType: word;
const aValue: variant): integer;
procedure Delete( const aIndex: integer );

TTiffGraphic = ....
property TiffTags: TTiffTags read ... write ...;
property TiffTagValue[ const aTag: word ]: variant read ... write ...;

It would allow to easy iterate through the tags in the current directory, having access to all relevant tag data and easy access to Tag Values.

2. fax2tiff
In the libtiff package is a application fax2tiff included. It allows to translate raw fax data files to TIFF files. If this would be included as a function reading from a stream, I could provide a new class allowing read of Winfax fax files by inheriting from tiff (mainly using libtiff decompression implementation). For this case it would be nice to implement a "protected" TCustomTiffGraphic where TTiffGraphic and TWinfaxGraphic inherit from.

3. Support for Sub-IFDs
TIFF allows sub-IFDs, currently used for Thumbnails or jpeg previews (becomes valueable if you have a 400MB graphic...). It would be valuable to being able to access this Sub-IFDs for read as well as for write.

And somthing more...

Envision could read strip-encoded tiffs. I would like to read and write strip as well as tile encoded tiffs...



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