feat: add watermarking functionality to weather art

- Include the image_processing gem to handle image manipulation
- Create a background worker for adding watermarks to weather art images
- Update WeatherArt model to attach watermark images
- Add a new watermark image asset

This commit enhances the WeatherArt feature by allowing images to
have watermarks added asynchronously, improving the visual
presentation of the art. It ensures sufficient image dimensions
before processing and includes error handling for the worker.

Gemfile

@@ -60,6 +60,8 @@ gem "aws-sdk-s3", "~> 1.177"
 gem "sidekiq", "~> 7.3"
 gem "sidekiq-scheduler", "~> 5.0"
 
+gem "image_processing", "~> 1.13"
+
 group :development, :test do
   # See https://guides.rubyonrails.org/debugging_rails_applications.html#debugging-with-the-debug-gem
   gem "debug", platforms: %i[ mri windows ], require: "debug/prelude"

Gemfile.lock

@@ -164,6 +164,7 @@ GEM
       multipart-post (~> 2.0)
     faraday-net_http (3.4.0)
       net-http (>= 0.5.0)
+    ffi (1.17.1-arm64-darwin)
     formtastic (5.0.0)
       actionpack (>= 6.0.0)
     formtastic_i18n (0.7.0)
@@ -183,6 +184,9 @@ GEM
       multi_xml (>= 0.5.2)
     i18n (1.14.6)
       concurrent-ruby (~> 1.0)
+    image_processing (1.13.0)
+      mini_magick (>= 4.9.5, < 5)
+      ruby-vips (>= 2.0.17, < 3)
     inherited_resources (1.14.0)
       actionpack (>= 6.0)
       has_scope (>= 0.6)
@@ -240,6 +244,7 @@ GEM
     matrix (0.4.2)
     meta-tags (2.22.1)
       actionpack (>= 6.0.0, < 8.1)
+    mini_magick (4.13.2)
     mini_mime (1.1.5)
     minitest (5.25.4)
     msgpack (1.7.5)
@@ -386,6 +391,9 @@ GEM
       faraday (>= 1)
       faraday-multipart (>= 1)
     ruby-progressbar (1.13.0)
+    ruby-vips (2.2.2)
+      ffi (~> 1.12)
+      logger
     ruby2_keywords (0.0.5)
     rubyzip (2.4.1)
     rufus-scheduler (3.9.2)
@@ -502,6 +510,7 @@ DEPENDENCIES
   down (~> 5.4)
   friendly_id (~> 5.5)
   httparty (~> 0.22.0)
+  image_processing (~> 1.13)
   jbuilder
   jsbundling-rails
   kamal

app/models/weather_art.rb

@@ -4,6 +4,7 @@ class WeatherArt < ApplicationRecord
 
   belongs_to :city
   has_one_attached :image
+  has_one_attached :image_with_watermark
 
   has_many :visits, class_name: "Ahoy::Visit", foreign_key: :weather_art_id
   has_many :events, class_name: "Ahoy::Event", foreign_key: :weather_art_id

app/workers/add_watermark_to_weatherart_worker.rb

@@ -0,0 +1,53 @@
+class AddWatermarkToWeatherArtWorker
+  include Sidekiq::Worker
+
+  def perform(weather_art_id)
+    @weather_art = WeatherArt.find_by(id: weather_art_id)
+    return unless @weather_art
+
+    add_watermark
+  rescue StandardError => e
+    Rails.logger.error "Error adding watermark to WeatherArt #{weather_art_id}: #{e.message}"
+    Rails.logger.error e.backtrace.join("\n")
+  end
+
+  private
+
+  attr_reader :weather_art
+
+  def add_watermark
+    return if weather_art.image_with_watermark.attached?
+
+    watermark_path = Rails.root.join("app/assets/images/today_ai_weather_copyright_watermark1.png")
+    return unless File.exist?(watermark_path)
+
+    image_tempfile = nil
+    watermark_tempfile = nil
+    begin
+      image_tempfile = weather_art.image.download
+      return unless image_dimensions_are_sufficient?(image_tempfile.path)
+
+      image = ImageProcessing::Vips.source(image_tempfile.path)
+      watermark = ImageProcessing::Vips.source(watermark_path)
+      watermarked_image = image.composite(watermark, "overlay")
+      watermark_tempfile = Tempfile.new([ "watermarked_image", ".png" ])
+      watermarked_image.write_to_file(watermark_tempfile.path)
+      weather_art.image_with_watermark.attach(
+        io: File.open(watermark_tempfile.path),
+        filename: "#{generate_filename("watermarked")}",
+        content_type: "image/png"
+      )
+    ensure
+      watermark_tempfile.unlink if watermark_tempfile
+    end
+  end
+
+  def image_dimensions_are_sufficient?(image_path)
+    dimensions = ImageProcessing::Vips.source(image_path).sizes
+    dimensions.width >= 200 && dimensions.height >= 200
+  end
+
+  def generate_filename(prefix)
+    "#{prefix}_#{weather_art.image.filename.base}"
+  end
+end