Hash references and Exif data

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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?

Comment on Hash references and Exif data

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Re: Hash references and Exif data by Minimiscience (Beadle) on Sep 06, 2007 at 23:33 UTC
`%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 `$image_info->{key}`. I don't know anything about EXIF, though.	[reply]
Re: Hash references and Exif data by sulfericacid (Deacon) on Sep 06, 2007 at 22:48 UTC
Can't help with the EXIF data but I suppose once it's in a format outside its original, it loses the fingerprints. For the hash reference, you have to create a k/v pair for each key inside of your referenced hash. Dirty. `while( my ($k, $v) = each %$image_info ) { print "key: $k, value: $v.\n"; }` [download] "Age is nothing more than an inaccurate number bestowed upon us at birth as just another means for others to judge and classify us" sulfericacid	[reply] [d/l]
Re: Hash references and Exif data by ikegami (Patriarch) on Sep 07, 2007 at 06:00 UTC
Where you'd use `%image_info` when using a hash, use `%$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	[reply] [d/l] [select]
Re: Hash references and Exif data by Gangabass (Vicar) on Sep 07, 2007 at 05:37 UTC
Try something like this: `my $image_info = $exif->get_image_info(); foreach my $key ( keys %{$image_info} ) { print $key, " => ", $image_info->{$key}, "\n"; }` [download]	[reply] [d/l]