0e901b2f84
Add methods to MediaFile to calculate the duration, frame count, and frame rate of animated GIFs, PNGs, Ugoiras, and videos. Some considerations: * It's possible to have a GIF or PNG that's technically animated but just has one frame. These are treated as non-animated images. * It's possible to have an animated GIF that has an unspecified frame rate. In this case we assume the frame rate is 10 FPS; this is browser dependent and may not be correct. * Animated GIFs, PNGs, and Ugoiras all support variable frame rates. Technically, each frame has a separate delay, and the delays can be different frame-to-frame. We report only the average frame rate. * Getting the duration of an APNG is surprisingly hard. Most tools don't have good support for APNGs since it's a rare and non-standardized format. The best we can do is get the frame count using ExifTool and the frame rate using ffprobe, then calculate the duration from that.
124 lines
3.3 KiB
Ruby
124 lines
3.3 KiB
Ruby
# A MediaFile for a JPEG, PNG, or GIF file. Uses libvips for resizing images.
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#
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# @see https://github.com/libvips/ruby-vips
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# @see https://libvips.github.io/libvips/API/current
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class MediaFile::Image < MediaFile
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# http://jcupitt.github.io/libvips/API/current/VipsForeignSave.html#vips-jpegsave
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JPEG_OPTIONS = { Q: 90, background: 255, strip: true, interlace: true, optimize_coding: true }
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# http://jcupitt.github.io/libvips/API/current/libvips-resample.html#vips-thumbnail
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THUMBNAIL_OPTIONS = { size: :down, linear: false }
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CROP_OPTIONS = { crop: :attention, linear: false }
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def dimensions
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image.size
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rescue Vips::Error
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[0, 0]
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end
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def is_corrupt?
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image.stats
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false
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rescue Vips::Error
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true
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end
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def duration
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if is_animated_gif?
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if metadata.has_key?("GIF:Duration")
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# GIF:Duration => "9.03 s"
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metadata["GIF:Duration"].to_f
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else
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# If GIF:Duration is absent then it means the GIF has an unlimited
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# framerate. In this situation we assume the browser will play the GIF
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# at 10 FPS; this is browser dependent.
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#
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# A GIF consists of a series of frames, each frame having a separate frame
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# delay. The duration of the GIF is the sum of each frame delay. If the frame
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# delay of each frame is zero, then it means the GIF has an unlimited framerate
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# and should be played as fast as possible. In reality, browsers cap the
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# framerate to around 10FPS.
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(frame_count * (1.0/10.0)).round(2)
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end
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elsif is_animated_png?
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frame_count.to_f / frame_rate
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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 frame_count
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if file_ext == :gif
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image.get("n-pages")
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elsif file_ext == :png
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metadata.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 frame_rate
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if is_animated_gif?
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frame_count / duration
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elsif is_animated_png?
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# XXX we have to resort to ffprobe to get the frame rate because libvips and exiftool can't get it.
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video.frame_rate
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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 channels
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image.bands
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end
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def colorspace
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image.interpretation
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end
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# @see https://github.com/jcupitt/libvips/wiki/HOWTO----Image-shrinking
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# @see http://jcupitt.github.io/libvips/API/current/Using-vipsthumbnail.md.html
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def preview(width, height)
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output_file = Tempfile.new(["image-preview", ".jpg"])
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resized_image = preview_frame.image.thumbnail_image(width, height: height, **THUMBNAIL_OPTIONS)
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resized_image.jpegsave(output_file.path, **JPEG_OPTIONS)
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MediaFile::Image.new(output_file)
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end
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def crop(width, height)
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output_file = Tempfile.new(["image-crop", ".jpg"])
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resized_image = preview_frame.image.thumbnail_image(width, height: height, **CROP_OPTIONS)
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resized_image.jpegsave(output_file.path, **JPEG_OPTIONS)
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MediaFile::Image.new(output_file)
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end
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def preview_frame
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if is_animated?
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FFmpeg.new(file).smart_video_preview
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else
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self
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end
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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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# @return [Vips::Image] the Vips image object for the file
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def image
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Vips::Image.new_from_file(file.path, fail: true).autorot
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end
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def video
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FFmpeg.new(file)
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end
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memoize :image, :video, :dimensions, :is_corrupt?, :is_animated_gif?, :is_animated_png?
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end
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