feat: add preset to create simple thumbnails

lib/ffmpeg.rb

@@ -21,6 +21,7 @@
 require_relative 'ffmpeg/presets/dash/aac'
 require_relative 'ffmpeg/presets/dash/h264'
 require_relative 'ffmpeg/presets/h264'
+require_relative 'ffmpeg/presets/thumbnail'
 require_relative 'ffmpeg/raw_command_args'
 require_relative 'ffmpeg/reporters/output'
 require_relative 'ffmpeg/reporters/progress'

lib/ffmpeg/filters/scale.rb

@@ -16,6 +16,51 @@ def scale(width: nil, height: nil, force_original_aspect_ratio: nil, flags: nil)
     # The Scale class uses the scale filter
     # to resize a multimedia stream.
     class Scale < Filter
+      class << self
+        # Returns a scale filter that fits the specified media
+        # within the specified maximum width and height,
+        # keeping the original aspect ratio.
+        #
+        # @param media [FFMPEG::Media] The media to fit.
+        # @param max_width [Numeric] The maximum width to fit.
+        # @param max_height [Numeric] The maximum height to fit.
+        # @return [FFMPEG::Filters::Scale] The scale filter.
+        def contained(media, max_width: nil, max_height: nil)
+          unless media.is_a?(FFMPEG::Media)
+            raise ArgumentError,
+                  "Unknown media format #{media.class}, expected #{FFMPEG::Media}"
+          end
+
+          if max_width && !max_width.is_a?(Numeric)
+            raise ArgumentError,
+                  "Unknown max_width format #{max_width.class}, expected #{Numeric}"
+          end
+
+          if max_height && !max_height.is_a?(Numeric)
+            raise ArgumentError,
+                  "Unknown max_height format #{max_height.class}, expected #{Numeric}"
+          end
+
+          return unless max_width || max_height
+
+          if media.rotated?
+            width = max_height || -2
+            height = max_width || -2
+          else
+            width = max_width || -2
+            height = max_height || -2
+          end
+
+          if width.negative? || height.negative?
+            Filters.scale(width:, height:)
+          elsif media.calculated_aspect_ratio > Rational(width, height)
+            Filters.scale(width:, height: -2)
+          else
+            Filters.scale(width: -2, height:)
+          end
+        end
+      end
+
       attr_reader :width, :height, :force_original_aspect_ratio, :flags
 
       def initialize(width: nil, height: nil, force_original_aspect_ratio: nil, flags: nil)

lib/ffmpeg/presets/dash/h264.rb

@@ -2,7 +2,6 @@
 
 require_relative '../../filter'
 require_relative '../../filters/fps'
-require_relative '../../filters/scale'
 require_relative '../../filters/split'
 require_relative '../dash'
 require_relative '../h264'

lib/ffmpeg/presets/h264.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require_relative '../filters/scale'
 require_relative '../preset'
 
 module FFMPEG
@@ -172,6 +173,14 @@ def initialize(
         max_height: nil,
         &
       )
+        if max_width && !max_width.is_a?(Numeric)
+          raise ArgumentError, "Unknown max_width format #{max_width.class}, expected #{Numeric}"
+        end
+
+        if max_height && !max_height.is_a?(Numeric)
+          raise ArgumentError, "Unknown max_height format #{max_height.class}, expected #{Numeric}"
+        end
+
         @audio_bit_rate = audio_bit_rate
         @video_preset = video_preset
         @video_profile = video_profile
@@ -225,28 +234,9 @@ def fits?(media)
       end
 
       def scale_filter(media)
-        unless media.is_a?(FFMPEG::Media)
-          raise ArgumentError,
-                "Unknown media format #{media.class}, expected #{FFMPEG::Media}"
-        end
-
         return unless @max_width || @max_height
 
-        if media.rotated?
-          width = @max_height || -2
-          height = @max_width || -2
-        else
-          width = @max_width || -2
-          height = @max_height || -2
-        end
-
-        if width.negative? || height.negative?
-          Filters.scale(width:, height:)
-        elsif media.calculated_aspect_ratio > Rational(width, height)
-          Filters.scale(width:, height: -2)
-        else
-          Filters.scale(width: -2, height:)
-        end
+        Filters::Scale.contained(media, max_width: @max_width, max_height: @max_height)
       end
     end
   end

lib/ffmpeg/presets/thumbnail.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+require_relative '../filters/scale'
+require_relative '../preset'
+
+module FFMPEG
+  # rubocop:disable Style/Documentation
+  module Presets
+    # rubocop:enable Style/Documentation
+    class << self
+      def thumbnail(
+        name: 'JPEG thumbnail',
+        filename: '%<basename>s.thumb.jpg',
+        metadata: nil,
+        max_width: nil,
+        max_height: nil
+      )
+        Thumbnail.new(
+          name:,
+          filename:,
+          metadata:,
+          max_width: max_width,
+          max_height: max_height
+        )
+      end
+    end
+
+    # Preset to create a thumbnail from a video.
+    class Thumbnail < Preset
+      attr_reader :max_width, :max_height
+
+      # @param name [String] The name of the preset.
+      # @param filename [String] The filename format of the output.
+      # @param metadata [Hash] The metadata to associate with the preset.
+      # @param max_width [Numeric] The maximum width of the thumbnail.
+      # @param max_height [Numeric] The maximum height of the thumbnail.
+      # @yield The block to execute to compose the command arguments.
+      def initialize(name: nil, filename: nil, metadata: nil, max_width: nil, max_height: nil, &)
+        if max_width && !max_width.is_a?(Numeric)
+          raise ArgumentError, "Unknown max_width format #{max_width.class}, expected #{Numeric}"
+        end
+
+        if max_height && !max_height.is_a?(Numeric)
+          raise ArgumentError, "Unknown max_height format #{max_height.class}, expected #{Numeric}"
+        end
+
+        @max_width = max_width
+        @max_height = max_height
+        preset = self
+
+        super(name:, filename:, metadata:) do
+          arg 'ss', (media.duration / 2).floor if media.duration.is_a?(Numeric)
+          arg 'frames:v', 1
+          filter preset.scale_filter(media)
+        end
+      end
+
+      def scale_filter(media)
+        return unless @max_width || @max_height
+
+        Filters::Scale.contained(media, max_width: @max_width, max_height: @max_height)
+      end
+    end
+  end
+end

spec/ffmpeg/filters/scale_spec.rb

@@ -13,6 +13,50 @@ module FFMPEG
 
   module Filters
     describe Scale do
+      describe '.contained' do
+        let(:media) { Media.new(fixture_media_file('[email protected]')) }
+
+        it 'raises ArgumentError if media is not an FFMPEG::Media' do
+          expect { described_class.contained(nil) }.to raise_error(ArgumentError)
+          expect { described_class.contained('media') }.to raise_error(ArgumentError)
+        end
+
+        it 'raises ArgumentError if max_width is not numeric' do
+          expect { described_class.contained(media, max_width: 'foo') }.to raise_error(ArgumentError)
+        end
+
+        it 'raises ArgumentError if max_height is not numeric' do
+          expect { described_class.contained(media, max_height: 'foo') }.to raise_error(ArgumentError)
+        end
+
+        it 'returns nil if max_width and max_height are not specified' do
+          expect(described_class.contained(media)).to be_nil
+        end
+
+        it 'returns a contained scale filter' do
+          expect(described_class.contained(media, max_width: 640).to_s).to eq('scale=w=640:h=-2')
+          expect(described_class.contained(media, max_height: 480).to_s).to eq('scale=w=-2:h=480')
+          expect(described_class.contained(media, max_width: 640, max_height: 480).to_s).to eq('scale=w=640:h=-2')
+        end
+
+        context 'when the media is rotated' do
+          let(:media) { Media.new(fixture_media_file('[email protected]')) }
+
+          it 'returns a contained scale filter' do
+            expect(described_class.contained(media, max_width: 640).to_s).to eq('scale=w=-2:h=640')
+            expect(described_class.contained(media, max_height: 480).to_s).to eq('scale=w=480:h=-2')
+            expect(described_class.contained(media, max_width: 640, max_height: 480).to_s).to eq('scale=w=-2:h=640')
+          end
+        end
+
+        context 'when the aspect ratio is higher than the max_width and max_height' do
+          it 'returns a contained scale filter that scales to width' do
+            expect(media).to receive(:calculated_aspect_ratio).and_return(2)
+            expect(described_class.contained(media, max_width: 640, max_height: 480).to_s).to eq('scale=w=640:h=-2')
+          end
+        end
+      end
+
       describe '#initialize' do
         it 'raises ArgumentError if width is not numeric or string' do
           expect { described_class.new(width: 1) }.not_to raise_error

spec/ffmpeg/media_spec.rb

@@ -3,17 +3,6 @@
 require_relative '../spec_helper'
 
 module FFMPEG
-  # Cache the ffprobe output for testing.
-  class << self
-    alias ffprobe_raw_capture3 ffprobe_capture3
-
-    def ffprobe_capture3(*args)
-      cache_key = args.hash
-      @ffprobe_cache ||= {}
-      @ffprobe_cache[cache_key] ||= ffprobe_raw_capture3(*args)
-    end
-  end
-
   describe Media do
     let(:load) { true }
     let(:autoload) { true }

spec/ffmpeg/presets_spec.rb

@@ -69,6 +69,16 @@ def initialize(name:, preset:, assert:)
           expect(media.audio_streams.length).to be(1)
           expect(media.audio_bit_rate).to be_within(15_000).of(128_000)
         end
+      ),
+      PresetTest.new(
+        name: 'JPEG thumbnail',
+        preset: Presets.thumbnail(max_width: 640, max_height: 360),
+        assert: lambda do |media|
+          expect(media.path).to match(/\.jpg\z/)
+          expect(media.streams.length).to be(1)
+          expect(media.width).to be(360)
+          expect(media.height).to be(640)
+        end
       )
     ].each do |test|
       describe test.name do

spec/spec_helper.rb

@@ -12,7 +12,17 @@
 require 'webmock/rspec'
 require 'webrick'
 
-FFMPEG.logger = Logger.new(nil)
+module FFMPEG
+  class << self
+    alias ffprobe_raw_capture3 ffprobe_capture3
+
+    def ffprobe_capture3(*args)
+      cache_key = args.hash
+      @ffprobe_cache ||= {}
+      @ffprobe_cache[cache_key] ||= ffprobe_raw_capture3(*args)
+    end
+  end
+end
 
 RSpec.configure do |config|
   config.filter_run focus: true
@@ -94,4 +104,4 @@ def stop_web_server
 end
 
 FileUtils.rm_rf(tmp_dir)
-FileUtils.mkdir_p tmp_dir
+FileUtils.mkdir_p(tmp_dir)