Module: FilePipeline::FileOperations::ExifManipulable

Included in:
ExifRecovery, ExifRedaction, ExifRestoration, VersionedFile
Defined in:
lib/file_pipeline/file_operations/exif_manipulable.rb

Overview

Mixin with methods to facilitate work with Exif metadata.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.file_tags ⇒ Object

Returns an Array of tags to be ignored during comparison. These can be merged with an ExifManipulable including FileOperation’s options to skip tags (e.g. the skip_tags option in ExifRestoration).

The included tags relate to the file properties (e.g. filesize, MIME-type) that will have been altered by any prior operation, such as file format conversions.



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 16

def self.file_tags
  %w[FileSize FileModifyDate FileAccessDate FileInodeChangeDate
     FilePermissions FileType FileTypeExtension MIMEType]
end

.parse_tag_error(message) ⇒ Object

:nodoc:



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 21

def self.parse_tag_error(message) # :nodoc:
  /Warning: Sorry, (?<tag>\w+) is not writable/
    .match(message) { |match| match[:tag] }
end

.strip_path(str) ⇒ Object

:nodoc:



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 26

def self.strip_path(str) # :nodoc:
  str.sub(%r{ - /?(/|[-:.]+|\w+)+\.\w+$}, '')
end

Instance Method Details

#delete_tags(out_file, tags_to_delete) ⇒ Object

Redacts (deletes) all tags_to_delete in out_file.



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 31

def delete_tags(out_file, tags_to_delete)
  exif, = read_exif out_file
  values = exif.select { |tag| tags_to_delete.include? tag }
  values_to_delete = values.transform_values { nil }
  return 'Info: nothing to delete.' if values.empty?

  log, = write_exif out_file, values_to_delete
  [log, values]
end

#missing_exif_fields(this_exif, other_exif) ⇒ Object

Compares to hashes with exif tags and values and returns a hash with the tags that are present in other_exif but absent in this_exif.



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 44

def missing_exif_fields(this_exif, other_exif)
  other_exif.delete_if do |tag, _|
    this_exif.key?(tag) || options[:skip_tags].include?(tag)
  end
end

#parse_exif_errors(errs, values) ⇒ Object

:args: error_messages, exif

Takes an array of error_messages and a hash (exif) with tags and their values and parses errors where tags could not be written.

Returns an array with a log (any messages that were not errors where a tag could not be written) and data (a hash with any tags that could not be written, and the associated values from exif)



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 58

def parse_exif_errors(errs, values)
  errs.each_with_object(LogDataParser.template) do |message, info|
    errors, data = info
    tag = ExifManipulable.parse_tag_error(message)
    if tag
      data.store tag, values[tag]
      next info
    end
    errors << ExifManipulable.strip_path(message)
    info
  end
end

#read_exif(*files) ⇒ Object

Reads exif information for one or more files. Returns an array of hashes, one for each file, with tags and their values.



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 73

def read_exif(*files)
  file_paths = files.map { |f| File.expand_path(f) }
  results, errors = MultiExiftool.read file_paths
  raise 'Error reading Exif' unless errors.empty?

  results.map(&:to_h)
end

#write_exif(out_file, values) ⇒ Object

Writes values (a hash with exif tags as keys) to out_file.

Returns an array with a log (an array of messages - strings) and a hash with all tags/values that could not be written.



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# File 'lib/file_pipeline/file_operations/exif_manipulable.rb', line 85

def write_exif(out_file, values)
  writer = MultiExiftool::Writer.new
  writer.filenames = Dir[File.expand_path(out_file)]
  writer.overwrite_original = true
  writer.values = values
  return if writer.write

  parse_exif_errors(writer.errors, values)
end