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December 1994
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1994.12.23 16:11 "Re: retreiving GrayResponseCurve and undefined tag info", by Sam Leffler
To: tiff@sgihub.corp.sgi.com
Subject: retreiving GrayResponseCurve and undefined tag info
Cc: sam@giraffe.asd.sgi.com
Date: Fri, 23 Dec 1994 09:50:00 EST
From: koz@bluegill.syracuse.sgi.com (Bob Kozdemba)
Hi:
Is it possible to retreive the GrayResponseCurve array using libtiff ? I get
zeroes returned. Here are the code fragments. Any ideas ?
The short answer is no. GrayResponseCurve is a deprecated tag;
the write should be using the Colorimetry tags defined in the
TIFF 6.0 spec. The library reads the tag and discards it to
avoid generating a warning about an unknown tag. You can easily
add support back into your copy of the library.
short grayResponseCurve[256];
TIFFGetField(tif, TIFFTAG_GRAYRESPONSECURVE, grayResponseCurve);
I also need to retreive 32 bytes of info at TAG 65535, which is undefined. I
noticed that 'tiffdump' works, but it looks like 'tiffdump' does not use
TIFFGetField().
The library only understands a compiled-in set of tags. If you want
the value of this tag you'll need to add it in. Some day I'll get
around to rewriting the directory handling to keep unknown tags around.
Sam