ab3f35580f
Move the metadata parsing code from MediaAsset to ExifTool::Metadata so we can use it outside the context of a MediaAsset, in particular when dealing with a MediaFile that hasn't been saved to disk yet.
126 lines
3.9 KiB
Ruby
126 lines
3.9 KiB
Ruby
require "shellwords"
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# A wrapper for the exiftool command.
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class ExifTool
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extend Memoist
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# @see https://exiftool.org/exiftool_pod.html#OPTIONS
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DEFAULT_OPTIONS = %q(
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-G1 -duplicates -unknown -struct --binary
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-x 'System:*' -x ExifToolVersion -x FileType -x FileTypeExtension
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-x MIMEType -x ImageWidth -x ImageHeight -x ImageSize -x MegaPixels
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).squish
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attr_reader :file
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# Open a file with ExifTool.
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#
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# @param file [File, String] an image or video file
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def initialize(file)
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@file = file.is_a?(String) ? File.open(file) : file
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end
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# Get the file's metadata.
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#
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# @param options [String] the options to pass to exiftool
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# @return [ExifTool::Metadata] the file's metadata
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def metadata(options: DEFAULT_OPTIONS)
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output = %x(exiftool #{options} -json #{file.path.shellescape})
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json = JSON.parse(output).first
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json = json.except("SourceFile")
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ExifTool::Metadata.new(json.with_indifferent_access)
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end
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memoize :metadata
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# A class representing the set of metadata returned by ExifTool for a file.
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# Behaves like a Hash, but with extra helper methods for interpreting the metadata.
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#
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# @see https://exiftool.org/TagNames/index.html
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class Metadata
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attr_reader :metadata
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delegate_missing_to :metadata
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# @param [Hash] a hash of metadata as returned by ExifTool
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def initialize(metadata)
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@metadata = metadata
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end
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def is_animated?
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frame_count.to_i > 1
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end
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def is_animated_gif?
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file_ext == :gif && is_animated?
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end
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def is_animated_png?
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file_ext == :png && is_animated?
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end
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# @see https://exiftool.org/TagNames/JPEG.html
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# @see https://exiftool.org/TagNames/PNG.html
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# @see https://danbooru.donmai.us/posts?tags=exif:File:ColorComponents=1
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# @see https://danbooru.donmai.us/posts?tags=exif:PNG:ColorType=Grayscale
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def is_greyscale?
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metadata["File:ColorComponents"] == 1 ||
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metadata["PNG:ColorType"] == "Grayscale" ||
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metadata["PNG:ColorType"] == "Grayscale with Alpha"
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end
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# https://exiftool.org/TagNames/EXIF.html
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def is_rotated?
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file_ext == :jpg && metadata["IFD0:Orientation"].in?(["Rotate 90 CW", "Rotate 270 CW", "Rotate 180"])
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end
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# Some animations technically have a finite loop count, but loop for hundreds
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# or thousands of times. Only count animations with a low loop count as non-repeating.
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def is_non_repeating_animation?
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loop_count.in?(0..10)
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end
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# @see http://www.vurdalakov.net/misc/gif/netscape-looping-application-extension
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# @see https://wiki.mozilla.org/APNG_Specification#.60acTL.60:_The_Animation_Control_Chunk
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# @see https://danbooru.donmai.us/posts?tags=-exif:GIF:AnimationIterations=Infinite+animated_gif
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# @see https://danbooru.donmai.us/posts?tags=-exif:PNG:AnimationPlays=inf+animated_png
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def loop_count
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return Float::INFINITY if metadata["GIF:AnimationIterations"] == "Infinite"
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return Float::INFINITY if metadata["PNG:AnimationPlays"] == "inf"
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return metadata["GIF:AnimationIterations"] if has_key?("GIF:AnimationIterations")
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return metadata["PNG:AnimationPlays"] if has_key?("PNG:AnimationPlays")
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# If the AnimationIterations tag isn't present, then it's counted as a loop count of 0.
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return 0 if is_animated_gif? && !has_key?("GIF:AnimationIterations")
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nil
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end
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def frame_count
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if file_ext == :gif
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fetch("GIF:FrameCount", 1)
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elsif file_ext == :png
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fetch("PNG:AnimationFrames", 1)
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else
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nil
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end
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end
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def file_ext
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if has_key?("File:ColorComponents")
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:jpg
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elsif has_key?("PNG:ColorType")
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:png
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elsif has_key?("GIF:GIFVersion")
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:gif
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elsif has_key?("QuickTime:MovieHeaderVersion")
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:mp4
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elsif has_key?("Matroska:DocType")
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:webm
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elsif has_key?("Flash:FlashVersion")
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:swf
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elsif has_key?("ZIP:ZipCompression")
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:ugoira
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end
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end
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end
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end
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