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June 2012
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2012.06.17 19:47 "Re: Tiff Digest, Vol 97, Issue 5", by He Yang
On 6/17/2012 12:00 PM, tiff-request@lists.maptools.org wrote: > Send Tiff mailing list submissions to > tiff@lists.maptools.org > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.maptools.org/mailman/listinfo/tiff > or, via email, send a message with subject or body 'help' to > tiff-request@lists.maptools.org > > You can reach the person managing the list at > tiff-owner@lists.maptools.org > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Tiff digest..." > > > Today's Topics: > > 1. Re: about the TIFFSetField usage (Frank Warmerdam) > 2. another problem about TIFFSetField Precision (He Yang) > 3. Re: another problem about TIFFSetField Precision > (Andreas Kleinert) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Sat, 16 Jun 2012 10:00:36 -0700 > From: Frank Warmerdam<warmerdam@pobox.com> > Subject: Re: [Tiff] about the TIFFSetField usage > To: tiff@lists.maptools.org > Message-ID:<4FDCBBB4.8050600@pobox.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > On 12-06-16 09:37 AM, He Yang wrote: >> Hi >> I am a beginner, an try to learn how to use TIFFSetField usage, I >> try to use TIFFSetField as below >> >> TIFFSetField(tif, tag, count, vlaue_ptr); >> it works, but the value is not correct when I try to use TIFFGetField >> , the count = 1, and the vlaue_ptr is the pointer of a short value, >> which value equal to 16, but when I read it back it become 1. What I >> did wrong? > He Yang, > > The tricky thing with TIFFSetField() is that the calling sequence is very > much determined by which tag you are getting and setting. The library > attempts to provide a "natural" calling sequence depending on the nature > of the tag but this means you need to lookup the particular tag in the > TIFFSetField man page to see the appropriate arguments. Likewise with > TIFFGetField. So you will need to be more specific about the tag you > are talking about. > > Best regards, Hi Frank I am trying to set the EXIFTAG_EXPOSURETIME, which is a TIFF_RATIONAL, is there are way to make sure the forward /backward conversion are always consistent. Does libtiff provide a way to make sure the rational to float and float to rational, But from my tracing, I found the precision was lost during read back from the disk file not from the memory? Best regards,