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August 2006
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2006.08.11 15:00 "Re: Newbie RICHTIFFIPTC query", by Dermot Paikkos
Hi, On 11 Aug 2006 at 10:15, Sean Burke wrote: > Hey. > According to the man page on TIFFGetField, TIFFTAG_RICHTIFFIPTC > returns two parameters: a count variable (uint32) and a point to an > array (void*). Sooooo..... Your primitive should look something like > this: uint32 *myCount; //depending on what your data looks like, one > of the following. // since you are using strcat, I assume that you > will want the first one char *myData; uint16 *myData; uint32 *myData; The data types is one of the problems, I am not sure how to determine what type of data I have in myData. There is character data in there somewhere but I am unable to find a way to assign it so I can compare it. If I use char *data I do avoid the "void reference" error though. The information at http://www.awaresystems.be/imaging/tiff/tifftags/iptc.html says: IFD Image Code 33723 (hex 0x83BB) Name IPTC LibTiff name TIFFTAG_RICHTIFFIPTC Type UNDEFINED or BYTE Count N Default None Presumably count is the size of the data in bytes. So I should loop through data until = count to slurp up the contents of data. But count in my test file is -17231916, how can I loop through that? > TIFFGetField(tif, TIFFTAG_RICHTIFFIPTC, myCount, myData); > > Also, if your data is actually a string, the strcat is unnecessary > since C treats all strings as char arrays. Try putting the following > line in to see if you need strcat: > > Finally, (for my own selfish reasons) what the heck is an IPTC? IPTC is just one of a few ways to embed data into a file. The IPTC format allows for an array of keywords, date created, captions and copyright. Thanx for the help. Dp. > Sean > > Beginner wrote: > > Hi, > > > > First off, I am very in-experienced with C. > > > > I would like to be able to retieve the IPTC data from a TIFF file. I > > have managed to get fairly close to my goal thanx to reading the > > archives but I need a bit of help and hopefully some explanations of > > what is wrong. > > > > The program below compiles (GCC 3.4.2) with the error: > > warning: dereferencing `void *' pointer > > > > The IPTC was addded to the TIFF file via PhotoShop 7, so it pre-XMP. > > When it runs I do get all the text I put into the file but it seg > > faults. I think the fault is because I strcat data that doesn't > > exist > > > > in my loop. What I'd like is some way to 1) to know where to start > > reading the data from 2) who to check the data is text that come > > from data, 3) any other suggested sanity checks anyone can think of. > > > > Is that a tall order? If so sorry but the books I have are not > > really helping me understand how to deal with a void pointers. > > > > TIA. > > > > > > ============= > > > > include <stdio.h> > > include <tiffio.h> > > > > > > main() > > > > int i; > > uint16 count; /* unit32 gives me no text at all */ > > void *data; > > char iptc_data[600]; > > > > TIFF* tif = TIFFOpen("test.tif", "r"); > > if (tif == NULL) { > > printf("Failed to open file\n"); > > exit(8); > > } > > if (TIFFGetField(tif, TIFFTAG_RICHTIFFIPTC, &count, &data) == 0) { > > printf("No IPTC Tag found\n"); > > exit(8); > > } > > printf("Size of IPTC Tag is %d bytes. %s.\n", count , &data); > > > > for ( i = 0; i < count; ++i) { > > strcat(iptc_data, &data[i]); > > } > > > > printf("%s\n", iptc_data); > > TIFFClose(tif); > > return 0; > > } > > > > ================= > > _______________________________________________ > > Tiff mailing list: Tiff@lists.maptools.org > > http://lists.maptools.org/mailman/listinfo/tiff > > http://www.remotesensing.org/libtiff/ > > > > -- > Sean Burke > Imaging Analysis Specialist > Albert Einstein College of Medicine > 1300 Morris Park Avenue > Bronx, NY 10461 > PH: 718.430.8628 > >