Module: Metaclean::Strategy

Defined in:
lib/metaclean/strategy.rb

Constant Summary collapse

PRIVACY_GROUP_PREFIXES =

Group-name PREFIXES treated as privacy-bearing. Matching whole families by prefix keeps the residual check fail-closed instead of an exact allowlist that silently misses variants:

GPS*       — GPS plus any sub-group
XMP-*      — every XMP namespace (XMP-exif GPS, XMP-mwg-rs face/person
             names, XMP-xmpMM DocumentID, XMP-iptcExt, …)
MakerNotes*, IPTC*
IFD1       — the embedded thumbnail IFD; a surviving thumbnail can carry
             the original's full EXIF+GPS

Over-flagging here is deliberate: for a privacy tool a false “still present” is far cheaper than a false “Cleaned”. (ICC colour-profile groups are intentionally NOT flagged — a colour profile isn’t PII; any genuinely identifying field such as Copyright is still caught by PRIVACY_TAGS below.)

%w[GPS XMP- MakerNotes IPTC IFD1].freeze
MAT2_ESSENTIAL =

Formats where ExifTool alone leaves document-internal metadata that only mat2’s rebuild removes (and which ExifTool also can’t fully re-read to verify). If mat2 won’t run for one of these, the runner warns that coverage is reduced rather than reporting a confident “Cleaned”.

%w[pdf docx xlsx pptx odt ods odp odg odf epub].freeze
PRIVACY_TAGS =

Specific tag NAMES (regardless of group) we never want to leak. If exiftool reports e.g. “EXIF:Artist” we still flag it because of the tag-name match, not the group. exiftool’s ‘-all=` normally strips these, so this list is a fail-closed BACKSTOP: if any survive a strip we’d rather over-warn than report a confident “Cleaned”.

%w[
  Artist Author Creator Copyright Rights
  By-line By-lineTitle Credit Source Contact OwnerName
  CameraOwnerName SerialNumber InternalSerialNumber LensSerialNumber
  Software HostComputer ProcessingSoftware
  ImageDescription UserComment
  LastModifiedBy LastSavedBy LastAuthor
  Make Model LensModel DateTimeOriginal CreateDate
  Title Subject Keywords Description Category Producer Company Manager
  CreationDate ModDate
  XPAuthor XPComment XPSubject XPKeywords XPTitle Comment
].freeze
MAT2_PREFERRED =

File extensions where mat2 is meaningfully stricter than ExifTool and should run first. For other formats, ExifTool is the broader expert.

%w[
  pdf docx xlsx pptx odt ods odp odg odf epub png svg
  mp4 avi mkv mov webm
].freeze

Class Method Summary collapse

Class Method Details

.mat2_essential?(path) ⇒ Boolean

Does this path need mat2 for adequate coverage? (See MAT2_ESSENTIAL.)

Returns:

  • (Boolean) 


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# File 'lib/metaclean/strategy.rb', line 125

def mat2_essential?(path)
  MAT2_ESSENTIAL.include?(File.extname(path).downcase.delete('.'))
end

.privacy_group?(group) ⇒ Boolean

A group is privacy-bearing if it matches one of the family prefixes (GPS, XMP-, MakerNotes, IPTC, IFD1).

Returns:

  • (Boolean) 


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# File 'lib/metaclean/strategy.rb', line 113

def privacy_group?(group)
  PRIVACY_GROUP_PREFIXES.any? { |p| group.to_s.start_with?(p) }
end

.privacy_residual(meta) ⇒ Object

Looks at metadata read AFTER cleaning and returns the entries that still look privacy-relevant. The runner uses this for the “still present” warning at the end of each file.

Why both group-match and tag-match? Tag names can appear under different groups depending on the format (e.g. “Author” in PDF vs “Artist” in EXIF). Combining the two keeps coverage broad without having to enumerate every tag pair.



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# File 'lib/metaclean/strategy.rb', line 98

def privacy_residual(meta)
  meta.select do |k, _|
    # Skip SourceFile and the System/File/etc. groups — not user metadata.
    next false unless Display.embedded_key?(k)

    # ExifTool keys look like "GPS:GPSLatitude". Split on the first ":";
    # no "Group:" prefix means the whole key is the tag name.
    group, tag = k.to_s.split(':', 2)
    name = tag.nil? ? group.to_s : tag
    privacy_group?(group) || privacy_tag?(name)
  end
end

.privacy_tag?(tag) ⇒ Boolean

A tag is privacy-bearing if it’s in the exact list OR is any GPS* tag (GPSLatitude/GPSLongitude/GPSPosition/… regardless of group).

Returns:

  • (Boolean) 


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# File 'lib/metaclean/strategy.rb', line 119

def privacy_tag?(tag)
  t = tag.to_s
  PRIVACY_TAGS.include?(t) || t.start_with?('GPS')
end

.tools_for(path) ⇒ Object

Returns an ordered list of tool symbols (e.g. ‘[:mat2, :exiftool, :qpdf]`) to run on `path`. The runner executes them in order; if one fails or is skipped, the next still runs. The three tools are always used together for maximum coverage — there is no per-tool opt-out; a tool that isn’t installed is simply left out (the ‘.available?`/`.supports?` checks).



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# File 'lib/metaclean/strategy.rb', line 65

def tools_for(path)
  ext = File.extname(path).downcase.delete('.')
  tools = []

  if ext == 'pdf'
    # PDFs benefit from all three, in this order:
    #   mat2 → cleans the high-level metadata + content streams it knows
    #   exiftool → strips the Info dictionary (Author, Title, Producer)
    #   qpdf → rebuilds the file, dropping any unreferenced bits
    tools << :mat2 if Mat2.available?
    tools << :exiftool
    tools << :qpdf if Qpdf.available?
  elsif MAT2_PREFERRED.include?(ext) && Mat2.available?
    # Office docs, modern image/video containers — mat2 leads.
    tools << :mat2
    tools << :exiftool
  else
    # Everything else (JPEG, MP3, RAW, …) — ExifTool is the gold standard.
    tools << :exiftool
    tools << :mat2 if Mat2.supports?(path)
  end

  tools
end