libexif-devel

[Libexif-devel] [newbie] Write Exif Data to a jpg file

[Fabien P. <fp...@wa...>]

Hello,
I'm currently working on an application that needs to write Exif data 
(GPS) into a jpeg file.
Actually, I have a tiffRepresentation (the image data) and I want to add 
GPS info into this data, in order to save the whole in a jpg file.
I want to use libexif, but I can't understand the API, and the 
documentation is a bit poor... :)
I'm using libexif on Mac OS X, with a Cocoa (Objective-C) application, 
and libexif was compiled successfully yet.
Many thanks for any link or pointer you might give me ;)

fp12

Re: [Libexif-devel] [newbie] Write Exif Data to a jpg file

[Lutz <lu...@us...>]

On Tue, 2005-07-12 at 12:27 +0200, Fabien Poupineau wrote:
> I'm currently working on an application that needs to write Exif data=20
> (GPS) into a jpeg file.
> Actually, I have a tiffRepresentation (the image data) and I want to ad=
d=20
> GPS info into this data, in order to save the whole in a jpg file.
> I want to use libexif, but I can't understand the API, and the=20
> documentation is a bit poor... :)

Agreed. Perhaps the code in libexif/test/test-mem.c can help you to
understand the syntax.

Does the image already have EXIF data?

Regards
--=20
Lutz M=FCller <lu...@us...>

Re: [Libexif-devel] [newbie] Write Exif Data to a jpg file

[Fabien P. <fp...@ma...>]

Lutz M=FCller a =E9crit :

>On Tue, 2005-07-12 at 12:27 +0200, Fabien Poupineau wrote:
> =20
>
>>I'm currently working on an application that needs to write Exif data=20
>>(GPS) into a jpeg file.
>>Actually, I have a tiffRepresentation (the image data) and I want to ad=
d=20
>>GPS info into this data, in order to save the whole in a jpg file.
>>I want to use libexif, but I can't understand the API, and the=20
>>documentation is a bit poor... :)
>>   =20
>>
>
>Agreed. Perhaps the code in libexif/test/test-mem.c can help you to
>understand the syntax.
>
> =20
>
I take a look now...

>Does the image already have EXIF data?
> =20
>
Actually no, I get the GPS info from another source and I have to put=20
then into an image without any EXIF info.

Regards.

Re: [Libexif-devel] [newbie] Write Exif Data to a jpg file

[Fabien P. <fp...@ma...>]

Lutz M=FCller a =E9crit :

>On Tue, 2005-07-12 at 12:27 +0200, Fabien Poupineau wrote:
> =20
>
>>I'm currently working on an application that needs to write Exif data=20
>>(GPS) into a jpeg file.
>>Actually, I have a tiffRepresentation (the image data) and I want to ad=
d=20
>>GPS info into this data, in order to save the whole in a jpg file.
>>I want to use libexif, but I can't understand the API, and the=20
>>documentation is a bit poor... :)
>>   =20
>>
>
>Agreed. Perhaps the code in libexif/test/test-mem.c can help you to
>understand the syntax.
> =20
>
I read this file, but I still don't understand how do you assign the=20
values to the tags: if I want to set the GPSLongitudeRef to east, what=20
do I have to do ?
I think I get how you save the exif data with the jpg data, but it lacks=20
me the setting of the tags...

Hoping for your answer,
Thanks.

Re: [Libexif-devel] [newbie] Write Exif Data to a jpg file

[Lutz <lu...@us...>]

On Wed, 2005-07-13 at 15:06 +0200, Fabien Poupineau wrote:
> I read this file, but I still don't understand how do you assign the
> values to the tags: if I want to set the GPSLongitudeRef to east, what
> do I have to do ?=20

There is no interface for that. You need to access the ExifEntry->data
directly, i.e.

e =3D exif_entry_new ();
exif_content_add_entry (c, e);
e->tag =3D EXIF_TAG_GPS_...;
e->format =3D EXIF_FORMAT_SHORT;
e->components =3D 1;
e->size =3D ...;
e->data =3D malloc (...):
exif_set_short (e->data, byte_order, ...);

Or similar (I don't know what format the individual tags have -> EXIF
specification).

Regards
--=20
Lutz M=FCller <lu...@us...>