Module: Metaclean::Exiftool

Defined in:
lib/metaclean/exiftool.rb

Overview

‘module Exiftool` (vs `class`) because we want module-level methods like `Exiftool.read(path)` — there’s no state to carry per instance.

Class Method Summary collapse

Class Method Details

.available? ⇒ Boolean

Returns true if ‘exiftool` is on PATH. The result is memoized in `@available` so repeated checks don’t re-spawn the process.

‘defined?(@available)` is safer than `@available.nil?` because the cached value could legitimately be `false` — we want to skip the re-check in that case too.

Returns:

  • (Boolean) 


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# File 'lib/metaclean/exiftool.rb', line 31

def available?
  return @available if defined?(@available)

  _out, _err, status = Open3.capture3('exiftool', '-ver')
  @available = status.success?
rescue Errno::ENOENT
  # `Errno::ENOENT` ("no such file or directory") is what Open3 raises
  # when the executable can't be found. We treat that as "not available".
  @available = false
end

.ensure_available! ⇒ Object

Hard-fail with a helpful install hint. Called from ‘read`/`strip!` before any work, so users see one clear message instead of a low-level Errno. The `<<~MSG … MSG` is a “squiggly heredoc”: leading indentation is stripped automatically, so the output is left-aligned.

Raises:



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# File 'lib/metaclean/exiftool.rb', line 56

def ensure_available!
  return if available?

  raise ExiftoolMissing, <<~MSG
    ExifTool is not installed or not on PATH.

    Install:
      macOS:    brew install exiftool
      Debian:   sudo apt install libimage-exiftool-perl
      Fedora:   sudo dnf install perl-Image-ExifTool
      Arch:     sudo pacman -S perl-image-exiftool
      Windows:  scoop install exiftool   (or download exiftool.org)
  MSG
end

.read(path) ⇒ Object

Reads metadata from a file and returns a flat Hash of “Group:Tag” => value.

ExifTool flag glossary:

-j         JSON output (machine-parseable)
-G1        Include the family-1 group name (e.g. "EXIF", "GPS", "IPTC")
-a         Allow duplicate tags (some formats have several with same name)
-u         Include unknown/unidentified tags
-s         Short tag names (no descriptions)
-n         Numeric values (no human formatting like "1/100 sec")
-api largefilesupport=1   Allow files >4 GB



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# File 'lib/metaclean/exiftool.rb', line 81

def read(path)
  ensure_available!
  out, err, status = Open3.capture3(
    'exiftool', '-j', '-G1', '-a', '-u', '-s', '-n', '-api', 'largefilesupport=1', path.to_s
  )
  raise Error, "ExifTool read failed: #{err.strip}" unless status.success?

  # ExifTool's JSON output is an array (one entry per file). We always
  # pass one file, so we take the first element. `|| {}` handles the
  # edge case where exiftool returns an empty array.
  data = JSON.parse(out)
  data.first || {}
rescue JSON::ParserError => e
  raise Error, "Could not parse ExifTool output: #{e.message}"
end

.strip!(path, keep_orientation: false, keep_color_profile: false) ⇒ Object

Removes every removable tag, in place. Returns true on success.

‘-all=` is the magic incantation: it sets every tag to nothing (= empty), which deletes them. `-overwrite_original` makes ExifTool replace the file directly instead of writing `file_original` next to it.

The optional ‘keep_*` flags are useful because:

* Orientation tells viewers how to rotate phone photos. Removing it
  can show the picture sideways.
* ICC profile tells viewers which color space the image is in.
  Removing it can shift colors.

Raises:



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# File 'lib/metaclean/exiftool.rb', line 108

def strip!(path, keep_orientation: false, keep_color_profile: false)
  ensure_available!

  preserving = keep_orientation || keep_color_profile
  args = ['exiftool', '-all=']

  # `-tagsFromFile @` says "copy tags from the same file you're writing
  # to". That sounds redundant, but combined with `-all=` running first,
  # it means "delete everything, then re-add only the listed tags".
  if preserving
    args.concat(['-tagsFromFile', '@'])
    args << '-Orientation' if keep_orientation
    args << '-ICC_Profile' if keep_color_profile
  end
  args.concat(['-overwrite_original', '-q', '-q', '-api', 'largefilesupport=1', path.to_s])

  _out, err, status = Open3.capture3(*args)
  return true if status.success?

  # Some minimal/odd files reject the preserve-pass. Fall back to a plain
  # full strip — but only if we *were* preserving, otherwise the retry
  # would be identical to the failed attempt.
  raise Error, "ExifTool strip failed: #{err.strip}" unless preserving

  _out2, err2, status2 = Open3.capture3(
    'exiftool', '-all=', '-overwrite_original', '-q', '-q', path.to_s
  )
  return true if status2.success?

  raise Error, "ExifTool strip failed: #{err2.strip.empty? ? err.strip : err2.strip}"
end

.version ⇒ Object

Returns the version string, or nil if exiftool is missing/broken.



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# File 'lib/metaclean/exiftool.rb', line 43

def version
  return nil unless available?

  out, _err, status = Open3.capture3('exiftool', '-ver')
  status.success? ? out.strip : nil
rescue Errno::ENOENT
  nil
end