2003.12.26 11:51 "Re: [Tiff] writing custom tags with TIFFSetField", by Andrey Kiselev

I am trying to update tiffcp to read and write a custom tag (Wang Annotations). Well, in the newest CVS it looks like TIFFGetField might be finally able to acquire the custom tag data. But when I try and write it using TIFFSetField it seems to be getting written to a different tag number than what was specified on the tag line. Beyond that, I can't figure out how writing to the TIFFTagValue that is specified in the default section of _TIFFVSetField actually writes to the new tiff directory. Has anyone seen any examples of reading and writing to custom tags using the new interface in 3.6.X?

Carl,

It is a bit tricky to modify tiffcp to enable custom tags copying. I'm recommend ti fill the feature request and shall try to implement such a feature in the next libtiff release.

I have attached an example code which shows how you can copy your tag.

Regards,
Andrey

Andrey V. Kiselev
Home phone: +7 812 5274898 ICQ# 26871517

#include <tiffio.h>
#include <stdio.h>

#define TIFFTAG_WANG 32932

static void TagExtender(TIFF *tiff)
{
    static const TIFFFieldInfo xtiffFieldInfo[] = {
        { TIFFTAG_WANG, -1, -1, TIFF_BYTE,  FIELD_CUSTOM,   1,  0,  "Wang" }
    };

    TIFFMergeFieldInfo(tiff, xtiffFieldInfo,
                       sizeof(xtiffFieldInfo) / sizeof(xtiffFieldInfo[0]));
}

int main(int argc, char **argv)
{
    TIFF    *in, *out;
    char    *buf, *wang;
    int     i, count;

    if (argc < 3)
    {
        fprintf(stderr, "Usage: %s in.tiff out.tiff\n", argv[0]);
        return 0;
    }

    /* Register the custom tag hadler */
    TIFFSetTagExtender(TagExtender);

    in = TIFFOpen(argv[1], "r");
    if (!in)
    {
        fprintf(stderr, "Can't open input file %s\n", argv[1]);
        return 1;
    }

    TIFFGetField(in, TIFFTAG_WANG, &count, &wang);

    out = TIFFOpen(argv[2], "w");
    if (!out)
    {
        fprintf(stderr, "Can't open output file %s\n", argv[2]);
        TIFFClose(in);
        return 2;
    }

    TIFFSetField(out, TIFFTAG_IMAGEWIDTH, 256);
    TIFFSetField(out, TIFFTAG_IMAGELENGTH, 256);
    TIFFSetField(out, TIFFTAG_BITSPERSAMPLE, 8);
    TIFFSetField(out, TIFFTAG_SAMPLESPERPIXEL, 3);
    TIFFSetField(out, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
    TIFFSetField(out, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
    TIFFSetField(out, TIFFTAG_WANG, count, wang);

    buf = _TIFFmalloc(3 * 256 * 256);
    TIFFWriteEncodedStrip(out, 0, buf, 3 * 256 * 256);
    _TIFFfree(buf);

    TIFFClose(out);
    TIFFClose(in);

    return 0;
}