#include <stdio.h>
#include <stdlib.h>
#include <FreeImage.h>

int main( int argc, char **argv ) {
    printf("%s\n", FreeImage_GetVersion());
    FIBITMAP *im = FreeImage_Load(FreeImage_GetFileType(argv[1], 0), argv[1], 0);
    printf("%d\n", im);

    FITAG *tag = FreeImage_CreateTag();
    FreeImage_SetTagKey(tag, "Urgency");
    FreeImage_SetTagLength(tag, 2);
    FreeImage_SetTagCount(tag, 2);
    FreeImage_SetTagType(tag, FIDT_ASCII);
    FreeImage_SetTagValue(tag, "5");
printf("*\n");
    FreeImage_SetMetadata(FIMD_IPTC, im, FreeImage_GetTagKey(tag), tag);
printf("*\n");
    FreeImage_DeleteTag(tag);
    FreeImage_Unload(im);
}

##</code><code>##

>convert wizard: wiz.jpg

>convert wizard: wiz.tif

>gcc -s -O2 -DWIN32 -fwrapv -fno-strict-aliasing -mms-bitfields -o fitest.exe fitest.c -lfreeimage

>fitest.exe wiz.jpg
3.18.0
2729184
*
*

>fitest.exe wiz.tif
3.18.0
2728264
*
*

##</code><code>##

use strict;
use warnings;
use FindBin;

load( $ARGV[0] );

use Inline C => config => inc => "-I$FindBin::Bin",
                          libs => "-L$FindBin::Bin -lfreeimage";
use Inline C => <<'END_OF_C';

#include <FreeImage.h>

void load(char *fname) {
//    FreeImage_Initialise(FALSE);
    printf("%s\n", FreeImage_GetVersion());
    FIBITMAP *im = FreeImage_Load(FreeImage_GetFileType(fname, 0), fname, 0);
    printf("%d\n", im);

    FITAG *tag = FreeImage_CreateTag();
    FreeImage_SetTagKey(tag, "Urgency");
    FreeImage_SetTagLength(tag, 2);
    FreeImage_SetTagCount(tag, 2);
    FreeImage_SetTagType(tag, FIDT_ASCII);
    FreeImage_SetTagValue(tag, "5");
printf("*\n");
    FreeImage_SetMetadata(FIMD_IPTC, im, FreeImage_GetTagKey(tag), tag);
printf("*\n");
    FreeImage_DeleteTag(tag);
    FreeImage_Unload(im);
//    FreeImage_DeInitialise();
}

END_OF_C

__END__

>perl fitest.pl wiz.jpg
3.18.0
2733096
*

>perl fitest.pl wiz.tif
3.18.0