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Image::Libexif cpan:FRITH last updated on 2018-07-17

Image-Libexif-0.0.2/

Image::Libexif

Image::Libexif - An interface to libexif.

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Example

High-level interface:

use v6;

use Image::Libexif :tagnames;
use Image::Libexif::Constants;

#| Prints all the EXIF tags
sub MAIN($file! where { .IO.f // die "file $file not found" })
{
  my Image::Libexif $e .= new: :$file;
  my @tags := $e.alltags: :tagdesc;
  say @tags».keys.flat.elems ~ ' tags found';
  for ^EXIF_IFD_COUNT -> $group {
    say "Group $group: " ~ «'Image info' 'Camera info' 'Shoot info' 'GPS info' 'Interoperability info'»[$group];
    for %(@tags[$group]).kv -> $k, @v {
      say "%tagnames{$k.Int}: @v[1] => @v[0]";
    }
  }
}
use v6;

use Concurrent::File::Find;
use Image::Libexif;
use Image::Libexif::Constants;

#| This program displays the EXIF date and time for every file in a directory tree
sub MAIN($dir where {.IO.d // die "$dir not found"})
{
  my @files := find $dir, :extension('jpg'), :exclude-dir('thumbnails') :file, :!directory;
  @files.race.map: -> $file {
      my Image::Libexif $e .= new: :file($file);
      try say "$file " ~ $e.lookup(EXIF_TAG_DATE_TIME_ORIGINAL); # don't die if no EXIF is present
      $e.close;
    }
}

Raw interface:

use v6;

use Image::Libexif::Raw;
use Image::Libexif::Constants;
use NativeHelpers::Blob;

#| This program extracts an EXIF thumbnail from an image and saves it into a new file (in the same directory as the original).
sub MAIN($file! where { .IO.f // die "file '$file' not found" })
{
  my $l = exif_loader_new() // die ’Can't create an exif loader‘;
  # Load the EXIF data from the image file
  exif_loader_write_file($l, $file);
  # Get the EXIF data
  my $ed = exif_loader_get_data($l) // die ’Can't get the exif data‘;
  # The loader is no longer needed--free it
  exif_loader_unref($l);
  $l = Nil;
  if $ed.data && $ed.size {
    my $thumb-name = $file;
    $thumb-name ~~ s/\.jpg/_thumb.jpg/;
    my $data = blob-from-pointer($ed.data, :elems($ed.size), :type(Blob));
    spurt $thumb-name, $data, :bin;
  } else {
    say "No EXIF thumbnail in file $file";
  }
  # Free the EXIF data
  exif_data_unref($ed);
}

For more examples see the example directory.

Description

Image::Libexif provides an interface to libexif and allows you to access the EXIF records of an image.

For more details on libexif see Lhttps://github.com/libexif and Lhttps://libexif.github.io/docs.html.

Documentation

use Image::Libexif;

use Image::Libexif :tagnames;

If asked to import the additional symbol tagnames, Image::Libexif will make available the Hash %tagnames, which has tag numbers as keys and a short description as values.

new()

Creates an Image::Libexif object.

If the optional argument $file is provided, then it will be opened and read; if not provided during the initialization, the program may call the open method later. If the optional argument data is provided, then the object will be initialized from the provided data; if not provided during the initialization, the program may call the load method later.

open(Str $file!)

Opens a file and reads it into an initialiazed object (when no file or data has been provided during initialization).

load(Buf $data!)

Reads the data into an initialiazed object (when no file or data has been provided during initialization).

close

Closes the internal libexif object, frees the memory and cleans up.

info(--> Hash)

Gathers some info:

lookup(Int $tag!, Int $group! --> Str)

lookup(Int $tag! --> Str)

Looks up a tag in a specific group or in all groups. A tag may be present in more than one group. Group names are available as constants:

tags(Int $group! where 0 <= * < 5, :$tagdesc? --> Hash)

Delivers all the tags in a specific group into a hash; the keys are the tag numbers. If the tag description is requested, the hash values are presented as an array [value, tag description].

alltags(:$tagdesc? --> Array)

Delivers an array of hashes, one for each group. If the tag description is requested, the hash values are presented as an array [value, tag description].

notes(--> Array)

Reads the Maker Note data as an array of strings. Each string is a concatenation of the note description, name, title, and value.

method thumbnail($file where { .IO.f // fail X::Libexif.new: errno => 1, error => "File $_ not found" } --> Blob)

sub thumbnail($file where { .IO.f // fail X::Libexif.new: errno => 1, error => "File $_ not found" } --> Blob) is export(:thumbnail)

Returns the thumbnail found in the original file, if any, as a Blob. This functionality is available as a method and a sub, since the library doesn't really need a fully initialized exif object. To use the sub import it explicitly: use Image::Libexif :thumbnail;.

Errors

There one case when an error may be returned: trying to open a non-existent file. This can happen while initializing an object with .new() and calling the .open() method. In both cases the method will return a Failure object, which can be trapped and the exception can be analyzed and acted upon.

Prerequisites

This module requires the libexif library to be installed. Please follow the instructions below based on your platform:

Debian Linux

sudo apt-get install libexif12

The module looks for a library called libexif.so.

Installation

To install it using zef (a module management tool):

$ zef update
$ zef install Image::Libexif

Testing

To run the tests:

$ prove -e "perl6 -Ilib"

Note

Image::Libexif relies on a C library which might not be present in one's installation, so it's not a substitute for a pure Perl6 module.

Author

Fernando Santagata

The Artistic License 2.0