Re: TIFF open error, tag 292 missing -- Envision Support Forum

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Date Posted: 17:53:13 09/11/00 Mon
Author: Michel
Subject: Re: TIFF open error, tag 292 missing
In reply to: Knud Boucher 's message, "Re: TIFF open error" on 12:05:07 09/07/00 Thu

Hi Knud,

I have located the problem. The file you sent me has many default tag
missings, one
in in particular, TIFFTAG_GROUP3OPTIONS = 292, which is the first time I
see a tiff file without this tag. Other tags, 296, 278 are also missing,
but Envision is using defaults for those tags.

Here is the new case statement in ReadDibFromTiffStream:

case CompressTag of
COMPRESSION_NONE : Dib.Compression := tcNone;
COMPRESSION_CCITTRLEW,
COMPRESSION_CCITTRLE : Dib.Compression := tcGroup3_1d;
COMPRESSION_CCITTFAX3 :
begin
try
TIFFGetField(TiffHandle, TIFFTAG_GROUP3OPTIONS,
Group3Options);
if (Group3Options and GROUP3OPT_2DENCODING) <> 0
then
Dib.Compression := tcGroup3_2d
else
Dib.Compression := tcGroup3_1d;
except
{ MB. Sep 11, 2000. Some fax 3 images don't specidy
1d or 2d, so
a default of 1d is used. I'm not sure if this is
valid
according to the tiff specification }
Dib.Compression := tcGroup3_1d;
end;

end;
COMPRESSION_CCITTFAX4 : Dib.Compression := tcGroup4;
COMPRESSION_PACKBITS : Dib.Compression := tcPackbits;
COMPRESSION_DEFLATE : Dib.Compression := tcZLib;
COMPRESSION_JPEG : Dib.Compression := tcJPEG;

else
raise ETiffError.Create(
Format(msgUnsupportedCompressionTag,
[CompressTag]));
end; { case }

Best regards,

Michel
> I know now that the files that give trouble are of
> type: G3FAX1D
> the ImageEn component of Encomp seems to handle them
> OK, but I would like to continue working with the
> Envision component.
>
> > When I open the multi pageTIFF file included in the
> > Examples in the demo app, everything works fine.
> > When I try to open a .tif file that I received from
> my
> > internet fax service I get:
> > ETiffError TIFFGetField: Tag = 296
> > 'WANG Imaging' included in windows has no trouble
> with
> > these files.
> > what could be the matter?

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