libexif-devel

[Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Many makernote tags are already documented by the 'exiftool' project 
[1], but are not in the libexif library. I'm working on adding those 
canon makernotes to the libexif library. I already figured out how to 
add entries for already existing tags, but I'm having trouble adding new 
tags.

In mnote-canon-tag.h, I define the new tag:

MNOTE_CANON_TAG_FOCAL_LENGTH = 0x2

And in mnote-canon-tag.c, I add the necessary human readable names to 
both tables. And in mnote-canon-entry.c, I add a section to the function 
mnote_canon_entry_get_value. I copied more or less the code from section 
MNOTE_CANON_TAG_SETTINGS_1 as a starting point:

case MNOTE_CANON_TAG_FOCAL_LENGTH:
    CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
    n = exif_get_short (data, entry->order) / 2;
    if (t >= n) return NULL;
    CC (entry->components, n, val, maxlen);
    vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
    snprintf (buf, sizeof (buf), "0x%04x", vs);
    strncpy (val, buf, maxlen - strlen (val));
    break;

But when I run the exif commandline utility, an error is reported for 
the new tag:

Focal type          |Invalid number of components (4, expected 1).

What am I doing wrong here?

[1] http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

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

Jef,

this message is printed by the CC macro. It checks whether
1st & 2nd arguments are equal. apparently entry->components is 4,
but n is only 1.

Hope this helps..

    -- Jan

> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>     n = exif_get_short (data, entry->order) / 2;
>     if (t >= n) return NULL;
>     CC (entry->components, n, val, maxlen);
>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>     snprintf (buf, sizeof (buf), "0x%04x", vs);
>     strncpy (val, buf, maxlen - strlen (val));
>     break;
>
> But when I run the exif commandline utility, an error is reported for
> the new tag:
>
> Focal type          |Invalid number of components (4, expected 1).
>
> What am I doing wrong here?
>
> [1] http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Jan Patera wrote:
>> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>>     n = exif_get_short (data, entry->order) / 2;
>>     if (t >= n) return NULL;
>>     CC (entry->components, n, val, maxlen);
>>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>>     snprintf (buf, sizeof (buf), "0x%04x", vs);
>>     strncpy (val, buf, maxlen - strlen (val));
>>     break;
>>
>> But when I run the exif commandline utility, an error is reported for
>> the new tag:
>>
>> Focal type          |Invalid number of components (4, expected 1).
>>
>> What am I doing wrong here?
> 
> 
> this message is printed by the CC macro. It checks whether
> 1st & 2nd arguments are equal. apparently entry->components is 4,
> but n is only 1.

I knew it was reported by the CC macro, but I don't understand why it is
happening. It is exactly the same code as is used for
MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but no
error there! Probably I forgot to add some code somewhere else, but I
don't see it.

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Marcus M. <mei...@su...>]

On Wed, Sep 06, 2006 at 03:39:30PM +0200, Jef Driesen wrote:
> Jan Patera wrote:
> >> case MNOTE_CANON_TAG_FOCAL_LENGTH:
> >>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
> >>     n = exif_get_short (data, entry->order) / 2;
> >>     if (t >= n) return NULL;
> >>     CC (entry->components, n, val, maxlen);
> >>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
> >>     snprintf (buf, sizeof (buf), "0x%04x", vs);
> >>     strncpy (val, buf, maxlen - strlen (val));
> >>     break;
> >>
> >> But when I run the exif commandline utility, an error is reported for
> >> the new tag:
> >>
> >> Focal type          |Invalid number of components (4, expected 1).
> >>
> >> What am I doing wrong here?
> > 
> > 
> > this message is printed by the CC macro. It checks whether
> > 1st & 2nd arguments are equal. apparently entry->components is 4,
> > but n is only 1.
> 
> I knew it was reported by the CC macro, but I don't understand why it is
> happening. It is exactly the same code as is used for
> MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but no
> error there! Probably I forgot to add some code somewhere else, but I
> don't see it.

Just a wild guess:
Did you adjust mnote_canon_entry_count_values() too?

Ciao, Marcus

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

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

Jef,

I inspected
http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html#FocalLength
and here is what I have found out:
1) MNOTE_CANON_TAG_FOCAL_LENGTH data is expected to be of the
EXIF_FORMAT_SHORT format and to have 4 items
2) the 1st value is FocalType, and not size of any kind.

Thus the correct sanity checks & code are:
   CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
   CC (entry->components, 4, val, maxlen);
   if (t >= 4) return NULL;
   vs = exif_get_short (entry->data + t * 2, entry->order);

Kind regards,
           Jan Patera

> Marcus Meissner wrote:
>> On Wed, Sep 06, 2006 at 03:39:30PM +0200, Jef Driesen wrote:
>>> Jan Patera wrote:
>>>>> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>>>>>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>>>>>     n = exif_get_short (data, entry->order) / 2;
>>>>>     if (t >= n) return NULL;
>>>>>     CC (entry->components, n, val, maxlen);
>>>>>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>>>>> snprintf (buf, sizeof (buf), "0x%04x", vs);
>>>>>     strncpy (val, buf, maxlen - strlen (val));
>>>>>     break;
>>>>>
>>>>> But when I run the exif commandline utility, an error is reported
>>>>> for the new tag:
>>>>>
>>>>> Focal type          |Invalid number of components (4, expected 1).
>>>>>
>>>>> What am I doing wrong here?
>>>>
>>>> this message is printed by the CC macro. It checks whether
>>>> 1st & 2nd arguments are equal. apparently entry->components is 4,
>>>> but n is only 1.
>>> I knew it was reported by the CC macro, but I don't understand why it
>>> is happening. It is exactly the same code as is used for
>>> MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but
>>> no error there! Probably I forgot to add some code somewhere else,
>>> but I don't see it.
>>
>> Just a wild guess:
>> Did you adjust mnote_canon_entry_count_values() too?
>
> I added an extra 'case MNOTE_CANON_TAG_FOCAL_LENGTH:' between the
> others.

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Jan Patera wrote:
>> Marcus Meissner wrote:
>>> On Wed, Sep 06, 2006 at 03:39:30PM +0200, Jef Driesen wrote:
>>>> Jan Patera wrote:
>>>>>> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>>>>>>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>>>>>>     n = exif_get_short (data, entry->order) / 2;
>>>>>>     if (t >= n) return NULL;
>>>>>>     CC (entry->components, n, val, maxlen);
>>>>>>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>>>>>> snprintf (buf, sizeof (buf), "0x%04x", vs);
>>>>>>     strncpy (val, buf, maxlen - strlen (val));
>>>>>>     break;
>>>>>>
>>>>>> But when I run the exif commandline utility, an error is reported
>>>>>> for the new tag:
>>>>>>
>>>>>> Focal type          |Invalid number of components (4, expected 1).
>>>>>>
>>>>>> What am I doing wrong here?
>>>>> this message is printed by the CC macro. It checks whether
>>>>> 1st & 2nd arguments are equal. apparently entry->components is 4,
>>>>> but n is only 1.
>>>> I knew it was reported by the CC macro, but I don't understand why it
>>>> is happening. It is exactly the same code as is used for
>>>> MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but
>>>> no error there! Probably I forgot to add some code somewhere else,
>>>> but I don't see it.
>>> Just a wild guess:
>>> Did you adjust mnote_canon_entry_count_values() too?
>> I added an extra 'case MNOTE_CANON_TAG_FOCAL_LENGTH:' between the
>> others.
> 
> I inspected
> http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html#FocalLength
> and here is what I have found out:
> 1) MNOTE_CANON_TAG_FOCAL_LENGTH data is expected to be of the
> EXIF_FORMAT_SHORT format and to have 4 items
> 2) the 1st value is FocalType, and not size of any kind.
> 
> I inspected
> http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html#FocalLength
> and here is what I have found out:
> 1) MNOTE_CANON_TAG_FOCAL_LENGTH data is expected to be of the
> EXIF_FORMAT_SHORT format and to have 4 items
> 2) the 1st value is FocalType, and not size of any kind.
> 
> Thus the correct sanity checks & code are:
>    CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>    CC (entry->components, 4, val, maxlen);
>    if (t >= 4) return NULL;
>    vs = exif_get_short (entry->data + t * 2, entry->order);

I assumed that tags always have a variable size and therefore always 
have a length field. Because entry->components has the correct 
information (without specifying this value myself), I assumed that it 
came from this first value.

In the exiftool documentation, all the offsets start at one (with the 
exception of this FocalLength tag), while in libexif numbering starts at 
zero. I assumed this FocalLength offset was a mistake in the 
documentation. I'll need to investigate this further.

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

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

Apparently the data associated to tag MNOTE_CANON_TAG_FOCAL_LENGTH have
four short int values (because entry->components is 4).
The first value is 2 (you get 1 after dividing by 2). Is this what
you expect? Are you familiar with the format of the data
of this tag (I am not)?

 -- Jan

 Apparent
> Jan Patera wrote:
>>> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>>>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>>>     n = exif_get_short (data, entry->order) / 2;
>>>     if (t >= n) return NULL;
>>>     CC (entry->components, n, val, maxlen);
>>>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>>> snprintf (buf, sizeof (buf), "0x%04x", vs);
>>>     strncpy (val, buf, maxlen - strlen (val));
>>>     break;
>>>
>>> But when I run the exif commandline utility, an error is reported for
>>> the new tag:
>>>
>>> Focal type          |Invalid number of components (4, expected 1).
>>>
>>> What am I doing wrong here?
>>
>>
>> this message is printed by the CC macro. It checks whether
>> 1st & 2nd arguments are equal. apparently entry->components is 4, but
>> n is only 1.
>
> I knew it was reported by the CC macro, but I don't understand why it is
> happening. It is exactly the same code as is used for
> MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but no
> error there! Probably I forgot to add some code somewhere else, but I
> don't see it.

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Marcus Meissner wrote:
> On Wed, Sep 06, 2006 at 03:39:30PM +0200, Jef Driesen wrote:
>> Jan Patera wrote:
>>>> case MNOTE_CANON_TAG_FOCAL_LENGTH:
>>>>     CF (entry->format, EXIF_FORMAT_SHORT, val, maxlen);
>>>>     n = exif_get_short (data, entry->order) / 2;
>>>>     if (t >= n) return NULL;
>>>>     CC (entry->components, n, val, maxlen);
>>>>     vs = exif_get_short (entry->data + 2 + t * 2, entry->order);
>>>>     snprintf (buf, sizeof (buf), "0x%04x", vs);
>>>>     strncpy (val, buf, maxlen - strlen (val));
>>>>     break;
>>>>
>>>> But when I run the exif commandline utility, an error is reported for
>>>> the new tag:
>>>>
>>>> Focal type          |Invalid number of components (4, expected 1).
>>>>
>>>> What am I doing wrong here?
>>>
>>> this message is printed by the CC macro. It checks whether
>>> 1st & 2nd arguments are equal. apparently entry->components is 4,
>>> but n is only 1.
>> I knew it was reported by the CC macro, but I don't understand why it is
>> happening. It is exactly the same code as is used for
>> MNOTE_CANON_TAG_SETTINGS_1 (which also has multiple components), but no
>> error there! Probably I forgot to add some code somewhere else, but I
>> don't see it.
> 
> Just a wild guess:
> Did you adjust mnote_canon_entry_count_values() too?

I added an extra 'case MNOTE_CANON_TAG_FOCAL_LENGTH:' between the others.

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Jef Driesen wrote:
> Many makernote tags are already documented by the 'exiftool' project 
> [1], but are not in the libexif library. I'm working on adding those 
> canon makernotes to the libexif library.
> 
> [1] http://www.sno.phy.queensu.ca/~phil/exiftool/TagNames/Canon.html

I finished updating the libexif library with canon makernotes. I have 
created three patches (mnote-canon-tag.h, mnote-canon-tag.c and 
mnote-canon-entry.c) against the cvs version. How do I contribute this work?

An overview of the changes:

* Some tags were updated from exiftool:
    - MNOTE_CANON_TAG_SETTINGS_1
    - MNOTE_CANON_TAG_SETTINGS_2
I also intended to change there names to some more meaningful values, 
like used in exiftool (respectively CAMERA_SETTINGS and SHOT_INFO), but 
I'm not sure if that will break existing applications. The only tag I 
did not update is the lenstype.

* Some new tags were added from exiftool:
    - MNOTE_CANON_TAG_FOCAL_LENGTH
    - MNOTE_CANON_TAG_PANORAMA

* All other tags (documented or not by exiftool) do not contain very 
useful information (for the only camera I own), and were not added. 
Maybe later, who knows...

* Added some internal functions to convert apex values to 
aperture/shutterspeed/iso values. Also moved the code for the table 
lookups to separate functions.

* Added a "Manual flash output" tag (actually there are two), obtained 
by reverse engineering. It works for my camera, but I don't know for others!

For some tags, exiftool lists exceptions for specific type of camera's. 
I did not incorporate that information, because I don't have those 
camera's to test. I checked everything very carefully, but there could 
still be some mistakes...

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Hubert F. <hu...@fi...>]

On Tuesday 12 September 2006 09:35, Jef Driesen wrote:
> I finished updating the libexif library with canon makernotes. I have
> created three patches (mnote-canon-tag.h, mnote-canon-tag.c and
> mnote-canon-entry.c) against the cvs version. How do I contribute this
> work?

cvd diff -u to the mailing list, as "attachment"


Hub

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

[Jef D. <jef...@ho...>]

Hubert Figuiere wrote:
> On Tuesday 12 September 2006 09:35, Jef Driesen wrote:
>> I finished updating the libexif library with canon makernotes. I have
>> created three patches (mnote-canon-tag.h, mnote-canon-tag.c and
>> mnote-canon-entry.c) against the cvs version. How do I contribute this
>> work?
> 
> cvd diff -u to the mailing list, as "attachment"

See attachment for the patch!

Re: [Libexif-devel] Need some help with adding support for extra canon makernotes

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

On Tue, 2006-09-12 at 20:45 +0200, Jef Driesen wrote:
> See attachment for the patch!

Applied. Thank you for your work!
--=20
Lutz M=FCller <lu...@to...>