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ruby + cairo + ffmpeg で砂嵐動画を作成する

Last updated at Posted at 2018-07-30

適当なダミー動画が欲しい時にこれでサクッと作成できます。

out.gif

cairo のインストール

$ gem install cairo

Rubyコード

suna.rb
require "cairo"

format = Cairo::FORMAT_ARGB32
# キャンバスの大きさ
width = 400
height = 300

surface = Cairo::ImageSurface.new format, width, height
context = Cairo::Context.new surface

# 1ピクセルの大きさ
cell_height = 2
cell_width = 2

# 解像度
num_cols = width / cell_width
num_rows = height / cell_height

66.times do |n|
  current_col = 0
  current_row = 0

  num_rows.times do |i|
    num_cols.times do |j|
      # ピクセルの座標
      y = i * cell_height
      x = j * cell_width
      # ランダムな色
      r = rand(100) / 100.0
      g = rand(100) / 100.0
      b = rand(100) / 100.0
      context.set_source_rgb r, g, b
      # ピクセルを描画
      context.rectangle x, y, cell_width, cell_height
      context.fill
    end
  end
  # ファイルに書き込み
  surface.write_to_png "out/suna#{format "%03d", n}.png"
end

連番画像を生成

$ ruby suna.rb

ffmpeg のインストール (Homebrew の場合)

$ brew install ffmpeg

ffmpeg で連番画像から動画を作成

$ ffmpeg -r 15 -i ./out/suna%03d.png -r 15 -an -vcodec libx264 -pix_fmt yuv420p out.mp4 
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