[Rails] OGP画像の作成をrmagickからimage_processing内のlibvipsに乗り換える

# Dockerfile
FROM ruby:3.2.1-slim
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev vim git imagemagick
# 以下省略

# Gemfile
gem 'mini_magick'

# app/models/post.rb
class Post < ApplicationRecord
  require 'mini_magick'

  OGP_BASE_IMAGE_PATH = './public/images/posts/ogp_base.png'.freeze
  OGP_GRAVITY = 'center'.freeze
  OGP_TEXT_POSITION = '0,0'.freeze
  OGP_FONT_PATH = './public/fonts/NotoSansJP-Bold.otf'.freeze
  OGP_FONT_SIZE = 70
  OGP_INDENTION_COUNT = 15
  OGP_ROW_LIMIT = 8
  OGP_TEXT_COLOR = 'white'.freeze

  def set_ogp_image
    image = create_image
    ogp_image.attach(io: StringIO.open(image.to_blob), filename: 'ogp.png')
  end

  private

  def create_image
    text = prepare_text(title.truncate(OGP_TRUNCATE_LENGTH))
    image = MiniMagick::Image.open(OGP_BASE_IMAGE_PATH)
    image.combine_options do |config|
      config.font OGP_FONT_PATH
      config.fill OGP_TEXT_COLOR
      config.gravity OGP_GRAVITY
      config.pointsize OGP_FONT_SIZE
      config.draw "text #{OGP_TEXT_POSITION} '#{text}'"
    end
    image
  end
end

# Dockerfile
FROM ruby:3.2.1-slim
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev vim git imagemagick libvips # libvipsを追加
# 以下省略

# Gemfile

# mini_magickを削除し、image_processingを追加
gem 'image_processing'

# app/models/post.rb
class Post < ApplicationRecord
  require 'image_processing/vips'

  OGP_BASE_IMAGE_PATH = './public/images/posts/ogp_base.png'.freeze
  OGP_FONT = 'Noto Sans JP 32'.freeze
  OGP_INDENTION_COUNT = 16
  OGP_TEXT_COLOR = [255, 255, 255].freeze
  OGP_TRUNCATE_LENGTH = 60
  OGP_ROW_LIMIT = 8
  OGP_DPI = 140

  def set_ogp_image
    image = create_image
    ogp_image.attach(io: StringIO.open(image.write_to_buffer('.png')), filename: 'ogp.png')
  end

  private

  def create_image
    base_image = Vips::Image.new_from_file(OGP_BASE_IMAGE_PATH)

    text_mask = Vips::Image.text(text, fontfile: OGP_FONT_PATH, font: OGP_FONT, dpi: OGP_DPI,
                                       width: base_image.width.to_i - 100, height: base_image.height.to_i - 100, align: 'centre')
    rgb = text_mask.new_from_image(OGP_TEXT_COLOR).copy(interpretation: 'srgb')
    text_image = rgb.bandjoin(text_mask)

    x = (base_image.width.to_i - text_image.width.to_i) / 2
    y = (base_image.height.to_i - text_image.height.to_i) / 2

    base_image.composite(text_image, 'over', x:, y:)
  end
end