Re: [Libexif-devel] listing headers

[Jan P. <pa...@pi...>]

> On Thu, Nov 6, 2008 at 10:22 PM, Jan Patera <pa...@pi...> wrote:
>>>     Longitude = 89.00, 40.00, 11.16
>>>
> (I would have expected a simple double printed though)

Well, this is what libexif does: it simply prints 3 doubles because
there are 3 values.

> What I haven't worked out yet is how to set 3 rationals.
>
>         entry_lon = exif_entry_new();
>         exif_entry_initialize(entry_lon, EXIF_TAG_GPS_LONGITUDE);
>
>         ExifRational value;
>         value.numerator = 54
>         value.denominator = 1;
>
>         exif_set_rational(entry_lon->data, exif_data_get_byte_order(ed),
> value);
>
>         exif_content_add_entry(ed->ifd[EXIF_IFD_GPS], entry_lon);
>
>         exif_entry_unref(entry_lon);
>
> According to the spec there are 3 rationals. But I have no idea how to
> do that with the API.
>
> May I ask for another pointer? :)

Hmm, did you read my second mail? Check what exif_entry_initialize does
for e.g. EXIF_TAG_EXIF_VERSION. You should either
1) adapt exif_entry_initialize so that it suports also GPS tags
  (currently it does not)
2) copy-past-adapt the code from exif_entry_initialize to your code:

 e->components = 3; // Use the correct number
 e->format = EXIF_FORMAT_xxxx; // Use correct format. RATIONAL?
 e->size = exif_format_get_size (e->format) * e->components;
 e->data = exif_entry_alloc (e, e->size);
 if (!e->data) fail;

 exif_set_rational(e->data, o, value1);
 exif_set_rational(e->data+sizeof(ExifRational), o, value2);
 exif_set_rational(e->data+2*sizeof(ExifRational), o, value3);

 -- Jan