[KimDaBa] EXIF tags

[Shawn Willden]

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On Saturday 03 January 2004 03:04 am, Jesper K. Pedersen wrote:
> Well if you could supply me with code for reading EXIF data, then we are
> a
long way, the rest I could easily handle.

Here's a snippet that retrieves date and time from EXIF tags and puts it 
into a QDateTime object.  Note that this code is derived from some that is 
known to work, but has been modified to remove it from its original 
context and hasn't been tested.  It should work, though ;-)

- -----------------------------------
#include <time.h>
#include <sys/time.h>
#include <libexif/exif-data.h>
#include <qdatetime.h>

QDateTime exifDateTime(QString filePathName) 
{	
    // Get date/time from EXIF tags
    ExifData* data = exif_data_new_from_file(filePathName.latin1());
    ExifEntry* entry = exif_content_get_entry(data->ifd[EXIF_IFD_EXIF], 
                                              EXIF_TAG_DATE_TIME_ORIGINAL);

    QDateTime exifDateTime;
    if (entry)
    {
        struct tm tmTime;
	strptime(exif_entry_get_value(entry), "%Y:%m:%d%t%T", &tmTime);
	exifDateTime.setTime_t(mktime(&tmTime));
    }

    exif_data_free(data);
    return exifDateTime;
}
- ---------------------------------------

> My greatest concern about all this EXIF stuff is to rely on 3rd party
> libraries.

I don't think libexif should be too much of a problem that way.  There are 
already a few bits of KDE that depend on it, plus lots of other apps that 
require it, like gphoto2 and the GIMP.  So although you'll want to add a 
config test to see that the libexif development files are available, 
libexif is almost certainly available anywhere that KimDaBa might go.

> | Another feature I'd like to add is the ability to change thumbnail
> | size on 
 the fly, with a pulldown box in the menubar.  Any comments
> | on this one?
>
> I'm not sure about the released version, but in the one in CVS,
> changing
 the size in the options dialog, and pressing OK, changes the
> size right away.
> I'm not sure how useful it would be to have the possibility to change
> stuff
 on the toolbar anyway - personally I've always only used one icon
> size, namly 128, which seems to be just perfect.

I find that I often want to use a 64px thumbnail for scanning large 
collections, but I want to bump it up to 128px or even 256px to see more 
details of a given image.  I tend to take lots of pictures of a given 
scene in order to get a really good one, so sometimes I need to get a 
better view.

Another approach, which might even be better, is to have a feature that 
pops up a larger version (say, 256px), along with the other data, similar 
to what Konqueror previewing does.  I suppose I could click on them to get 
a larger view, but that's slow.  Perhaps the viewer-sized images should be 
cached along with the thumbnails?

Thanks!

	Shawn.
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