AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2004.01.20 18:40 "[Tiff] Reading Custom Tags", by David Christopher Asher
2004.01.20 17:14 "Re: [Tiff] Reading Custom Tags", by Frank Warmerdam
2004.01.20 20:10 "Re: [Tiff] Reading Custom Tags", by Antonio Scuri
2004.01.20 20:46 "Re: [Tiff] Reading Custom Tags", by David Christopher Asher
2004.01.23 22:14 "RE: [Tiff] Reading Custom Tags", by Pushkar Pradhan
2004.01.24 00:50 "Re: [Tiff] Reading Custom Tags", by Antonio Scuri

2004.01.20 17:14 "Re: [Tiff] Reading Custom Tags", by Frank Warmerdam

I am having sime trouble reading custom tags from a TIFF file. The tags are two GeoTIFF tags, (33550 and 33922), which hold 3 doubles and 6 doubles respectively. I have found very little documentation on custom tags online, apart from the 3.6.0 spec notes page, which would seem to indicate you read them more or less like standard tags like TIFFTAG_IMAGEWIDTH.

So, I use something like:

    ...
    double x,y,z;
    TIFFGetField(tiff,33550,&x,&y,&z);
    ...

I am using version 3.6.0 of the library. Any help is appreciated!

Dave,

I think you will find you need 3.6.1. There was a grevious bug in the custom tag support in 3.6.0.

Second, the custom tags will use "generic" semantics as I recall. Basically you will need to pass the count (a u_short) and then the pointer to be initialized.

eg.

     double *xyz;
     u_short count;

     TIFFGetField( tiff, 33550, &count, &xyz );

     assert( count == 3 );
     printf( "x=%g, y=%g, z=%g\n", xyz[0], xyz[1], xyz[2] );

Best regards,

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent