AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

2003.09.25 10:45 "[Tiff] Extended rational tag.", by David Christopher

Hi,

I'm new to libtiff and have been trying to read values from an extended rational tag in a variant of a tiff file. I've used Niles' code for this and replaced his example tags with my own. However the values that I'm getting when I try to read the tag are nonsense. However, TIFFGetField doesn't return 0 so it suggests that it can find the tag ok. Hence I guess I haven't declared the correct data types in places.

I've copied the parts of the code that I've changed below. Can anybody tell me what I've done wrong?!

Regards

Dave Christopher

// from tif_dir.c
static const TIFFFieldInfo xtiffFieldInfo[] = {

  /* XXX Replace these example tags with your own
extended tags */
    { TIFFTAG_UIC3_STKINFO,  -1, -1, TIFF_RATIONAL, FIELD_UIC3_STKINFO, TRUE, TRUE, "UIC3STKTag" },
};

static int
_XTIFFVSetField(TIFF* tif, ttag_t tag, va_list ap)
{
   xtiff *xt = XTIFFDIR(tif);
      XTIFFDirectory* xd = &xt->xtif_dir;
     int status = 1;
 uint32 v32=0;
   int i=0, v=0;
   va_list ap1 = ap;

       /* va_start is called by the calling routine */

        switch (tag)
    {
               /*
                 * XXX put your extended tags here; replace the implemented
                 *     example tags with your own.
                 */
    case TIFFTAG_UIC3_STKINFO:
                xd->xd_uic3_stkinfo_size = (uint32) va_arg(ap, uint32);
/ *** in the long array here I've passed two * size as
I think size is the number of rationals, but I want
twice this number for the long array? *****/
            _TIFFsetLongArray( &xd->tag3_extra, (uint32*) va_arg(ap, uint32*), (long) 2*xd->xd_uic3_stkinfo_size );
         break;
  default:
                /* call the inherited method */
         return (PARENT(xt,vsetfield))(tif,tag,ap);
              break;
  }
       if (status) {
           /* we have to override the print method here,
            * after the compression tags have gotten to it.
                 * This makes sense because the only time we would
               * need the extended print method is if an extended
              * tag is set by the reader.
             */
             if (!(xt->xtif_flags & XTIFFP_PRINT))
           {
                       PARENT(xt,printdir) = TIFFMEMBER(tif,printdir);
                         TIFFMEMBER(tif,printdir) = _XTIFFPrintDirectory;
                        xt->xtif_flags |= XTIFFP_PRINT;
         }
               TIFFSetFieldBit(tif, _TIFFFieldWithTag(tif, tag)->field_bit);
           tif->tif_flags |= TIFF_DIRTYDIRECT;
     }
       va_end(ap);
     return (status);
}


static int
_XTIFFVGetField(TIFF* tif, ttag_t tag, va_list ap)
{
  xtiff *xt = XTIFFDIR(tif);
      XTIFFDirectory* xd = &xt->xtif_dir;

     switch (tag) {
          /*
                 * XXX put your extended tags here; replace the implemented
                 *     example tags with your own.
                 */
    case TIFFTAG_UIC3_STKINFO:

            *va_arg(ap, uint32*) = xd->xd_uic3_stkinfo_size;
               *va_arg(ap, uint32**) = xd->tag3_extra;
              break;
  default:
                /* return inherited method */
           return (PARENT(xt,vgetfield))(tif,tag,ap);
              break;
  }
       return (1);
}

/// From tiffiop.h
/* XXX - Define number of your extended tags here */
#define NUM_XFIELD 1
#define XFIELD_BASE (FIELD_LAST-NUM_XFIELD)

/*  XXX - Define your Tag Fields here  */
#define       FIELD_UIC3_STKINFO      (XFIELD_BASE+0)



/* XXX - Define Private directory tag structure here */
struct XTIFFDirectory
{
    uint32   xd_uic3_stkinfo_size;
 uint32*  tag3_extra;
};
typedef struct XTIFFDirectory XTIFFDirectory;