Hash references and Exif data

[Anonymous Monk]

Two questions.

I'm making an image gallery and am using Image::EXIF to extract the exif data. It produces a hash reference and up til now (years and years after using Perl) I've never in my life had to use a hash reference. I don't know how to break it into usable data. Can someone show me how I'd take %image_info (hash reference) and get data from it?

As far as EXIF, does this information disappear from an image if it's edited with PhotoShop, PaintShopPro, etc? Or is it semi-permanently attached to images?

[Minimiscience]

%image_info isn't the hash reference; $image_info is. References are stored as scalars, and in order to dereference them, you have to use special syntax. To treat the reference as a normal hash, write it as %$image_info, and to access just a single element from it, write $image_info->{key}.

I don't know anything about EXIF, though.

[ikegami]

Where you'd use %image_info when using a hash, use %$image_info instead.
Where you'd use $image_info{$key} when using a hash, use $image_info->{$key} instead.
It's that simple.

See Dereferencing Syntax
and References Quick Reference

[sulfericacid]

Can't help with the EXIF data but I suppose once it's in a format outside its original, it loses the fingerprints.

For the hash reference, you have to create a k/v pair for each key inside of your referenced hash. Dirty.

    while( my ($k, $v) = each %$image_info ) {
        print "key: $k, value: $v.\n";
    }

[Gangabass]

Try something like this:

my $image_info = $exif->get_image_info();
foreach my $key ( keys %{$image_info} ) {
    print $key, " => ", $image_info->{$key}, "\n";
}