Migrate image pipeline from RMagick to libvips (1.2.0)

Direct ruby-vips swap, no image_processing gem fallback, RMagick
dropped from the gemspec. Bumps CheesyGallery::VERSION to 1.2.0 so
the user-visible install change is signalled by SemVer.

* base_image_file.rb: `process_and_write` signature changes from
  `(img, dest_path)` to `(source_path, dest_path)`. The base class
  no longer opens the source file; the default body is `FileUtils.cp`
  and subclasses own decode+resize+write via `Vips::Image.thumbnail`.
  PR #416's `render_cache_discriminator` hook is preserved as-is.

* image_file.rb: ping path uses `Vips::Image.new_from_file(...).autorot`
  inside the Geometry-cache getset block. The cached `[h, w]` tuple
  is now stashed on the instance (@geometry) so `process_and_write`
  doesn't re-ping. Resize uses `Vips::Image.thumbnail(path, w, height:,
  size: :down, crop: :none)` — `size: :down` is the libvips analogue
  of PR #416's shrink-only `>` flag. JPEG written with `Q:`, `interlace:
  true`, `strip: true`, `optimize_coding: true`. `geometry_string` is
  preserved verbatim for cache-key fingerprint compatibility with
  PR #416; under libvips its value is decorative and only feeds the
  Geometry/Render cache keys. A new private `fit_inside` replicates
  the shrink-only WxH math in plain Ruby.

* image_thumb.rb: `Vips::Image.thumbnail(path, w, height: h,
  crop: :centre)` matches RMagick's `resize_to_fill!`. Thumbs now use
  the same size-optimisation flags as full-size renders, at Q80.

* cache_spec.rb: spies retargeted onto `Vips::Image.new_from_file` and
  `Vips::Image.thumbnail`. Counts stay numerically identical because
  cached geometry is threaded into `process_and_write` — there is
  still exactly one "ping" per source on a Geometry-cache miss and
  one fused decode+resize per variant on a Render-cache miss. The
  three-segment Geometry-key test and Render-discriminator test from
  PR #416 pass verbatim (the discriminator infrastructure is
  library-agnostic).

* generator_spec.rb: output-dimension verifiers swapped from
  `Magick::Image.ping(dest).first` to `Vips::Image.new_from_file(dest)
  .autorot`. PR #416's pinned dimensions `[1000, 750]` (default
  `1920x1080`, shrink-only) and `[533, 400]` (`600x400` override)
  match libvips under `fit_inside`.

* Gemfile.lock under spec/fixtures/test_site regenerated; ruby-vips
  2.3.0 replaces rmagick.

Behaviour changes are documented in CHANGELOG.md:
- EXIF Orientation is now honoured (libvips' `thumbnail` auto-rotates
  before downsample; output drops the orientation tag). Latent bug fix
  for sideways sources.
- Thumbnails are now progressive Q80 JPEGs with stripped metadata
  (was: RMagick defaults — baseline, ~Q75, EXIF retained).
- `max_size` flags other than `>` (i.e. `!`, `^`, `@`, `#`) are now
  silently treated as plain `WxH`. cheesy-gallery's own config never
  used them; full ImageMagick geometry syntax was out of scope.

Perf characterised in docs/libvips-bench.md: 3.35x faster on
DSLR-sized inputs, modest regression on web-sized inputs, RAM roughly
comparable. The migration is justified by the DSLR speedup plus
non-perf wins (escape from RMagick CVE / build-pain, correct EXIF
Orientation handling).

https://claude.ai/code/session_01AZQRrnPUpfUMCXLu3oTSDN

Author: claude

cheesy-gallery.gemspec

@@ -39,5 +39,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'rubocop'
 
   spec.add_dependency 'jekyll', '~> 4.4'
-  spec.add_dependency 'rmagick', '>= 4', '< 6'
+  spec.add_dependency 'ruby-vips', '~> 2.2'
 end

lib/cheesy-gallery/base_image_file.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
-require 'rmagick'
+require 'fileutils'
+require 'vips'
 
 # This StaticFile subclass adds additional functionality for images in the
 # gallery
@@ -19,8 +20,8 @@ def path
   end
 
   # overwrite this method to add additional processing
-  def process_and_write(img, path)
-    img.write(path) {}
+  def process_and_write(source_path, dest_path)
+    FileUtils.cp(source_path, dest_path)
   end
 
   # Skip the render when our content-aware Render-cache key says we've
@@ -57,17 +58,14 @@ def render_cache_discriminator
     ''
   end
 
-  # Replace Jekyll's StaticFile#copy_file (FileUtils.cp) with RMagick
+  # Replace Jekyll's StaticFile#copy_file (FileUtils.cp) with libvips
   # rendering. Super's write has already mkdir_p'd the parent and
-  # rm'd any existing dest_path before getting here.
+  # rm'd any existing dest_path before getting here. Subclasses do
+  # their own decode + resize + write via Vips::Image.thumbnail; the
+  # base no longer opens the source file itself.
   def copy_file(dest_path)
-    source = Magick::ImageList.new(path)
-    begin
-      Jekyll.logger.debug 'Rendering:', dest_path
-      process_and_write(source, dest_path)
-    ensure
-      source.destroy!
-    end
+    Jekyll.logger.debug 'Rendering:', dest_path
+    process_and_write(path, dest_path)
 
     unless File.symlink?(dest_path)
       File.utime(self.class.mtimes[path], self.class.mtimes[path], dest_path)

lib/cheesy-gallery/image_file.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'rmagick'
+require 'vips'
 require 'cheesy-gallery/base_image_file'
 
 # This StaticFile subclass adds additional functionality for images in the
@@ -16,44 +16,45 @@ def initialize(site, collection, file, max_size:, quality:)
 
     realpath = File.realdirpath(path)
     mtime = File.mtime(realpath)
-    geom = @@geometry_cache.getset("#{realpath}##{mtime}##{geometry_string}") do
-      result = [100, 100]
-      # read file metadata in the same way it will be processed
+    @geometry = @@geometry_cache.getset("#{realpath}##{mtime}##{geometry_string}") do
       Jekyll.logger.debug 'Identifying:', path
-      source = Magick::Image.ping(path).first
-      source.change_geometry!(geometry_string) do |cols, rows, _img|
-        result = [rows, cols]
-      end
-      source.destroy!
-      result
+      # autorot so width/height reflect post-orientation pixels — matches
+      # what Vips::Image.thumbnail will produce at render time.
+      source = Vips::Image.new_from_file(path, access: :sequential).autorot
+      fit_inside(source.width, source.height)
     end
 
-    data['height'] = geom[0]
-    data['width'] = geom[1]
+    data['height'] = @geometry[0]
+    data['width'] = @geometry[1]
   end
 
   # instead of copying, renders an optimised version
-  def process_and_write(img, path)
-    img.change_geometry!(geometry_string) do |cols, rows, i|
-      i.resize!(cols, rows)
-    end
-    # follow recommendations from https://stackoverflow.com/a/7262050/4918 to get better compression
-    img.interlace = Magick::PlaneInterlace
-    # but skip the blur to avoid too many changes to the data
-    # img.gaussian_blur(0.05)
-    img.strip!
-    # workaround weird {self} initialisation pattern
-    quality = @quality
-    img.write(path) { |image| image.quality = quality }
+  def process_and_write(source_path, dest_path)
+    target_h, target_w = @geometry
+    img = Vips::Image.thumbnail(
+      source_path,
+      target_w,
+      height: target_h,
+      size: :down, # never upscale — equivalent of the `>` in geometry_string
+      crop: :none,
+    )
+    img.write_to_file(
+      dest_path,
+      Q: @quality,
+      interlace: true,
+      strip: true,
+      optimize_coding: true,
+    )
   end
 
   private
 
-  # Append the `>` flag so `change_geometry!` fits originals into
-  # @max_size when they're larger, but never enlarges smaller ones —
-  # a photo gallery should not produce blurry upscales of small
-  # source images. Idempotent: skip the append if the user already
-  # supplied any ImageMagick geometry flag (!, <, >, ^, @, #).
+  # Preserved from the RMagick era. Under libvips this is no longer
+  # passed to an image library — its value is purely the cache
+  # fingerprint so that changing `max_size` (or upgrading to a release
+  # that changes the upscale policy) invalidates entries naturally.
+  # Idempotent: skip the `>` append if the user already supplied any
+  # ImageMagick geometry flag (!, <, >, ^, @, #).
   def geometry_string
     @geometry_string ||= @max_size.match?(%r{[!<>^@#]}) ? @max_size : "#{@max_size}>"
   end
@@ -64,4 +65,17 @@ def geometry_string
   def render_cache_discriminator
     geometry_string
   end
+
+  # Replicates the shrink-only `WxH>` semantics that the geometry
+  # string previously got from ImageMagick: fit inside the box,
+  # preserve aspect ratio, never upscale. Returns [height, width] to
+  # match the legacy Geometry-cache shape and the data hash. The
+  # ImageMagick-style trailing flags (`!`, `^`, `@`, `#`) are parsed
+  # out by `to_i`'s leading-digits rule and silently ignored — see
+  # CHANGELOG for the narrowing.
+  def fit_inside(src_width, src_height)
+    max_w, max_h = @max_size.split('x').map(&:to_i)
+    scale = [max_w.to_f / src_width, max_h.to_f / src_height, 1.0].min
+    [(src_height * scale).round, (src_width * scale).round]
+  end
 end

lib/cheesy-gallery/image_thumb.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require 'rmagick'
+require 'vips'
 require 'cheesy-gallery/base_image_file'
 
 # This StaticFile subclass represents thumbnail images for each image. On `write()` it renders a 150x150 center crop of the source
@@ -14,9 +14,20 @@ def initialize(site, collection, file, postfix, height, width)
     @width = width
   end
 
-  # instead of copying, renders the thumbnail
-  def process_and_write(img, path)
-    img.resize_to_fill!(height, width)
-    img.write(path)
+  # centre-crop square thumbnail, optimised for file size at Q80
+  def process_and_write(source_path, dest_path)
+    img = Vips::Image.thumbnail(
+      source_path,
+      width,
+      height: height,
+      crop: :centre,
+    )
+    img.write_to_file(
+      dest_path,
+      Q: 80,
+      interlace: true,
+      strip: true,
+      optimize_coding: true,
+    )
   end
 end

lib/cheesy-gallery/version.rb

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module CheesyGallery
-  VERSION = '1.1.1'
+  VERSION = '1.2.0'
 end

spec/cheesy/cache_spec.rb

@@ -4,7 +4,7 @@
 require 'jekyll'
 require 'fileutils'
 require 'tmpdir'
-require 'rmagick'
+require 'vips'
 
 # Cache behaviour specs for cheesy-gallery.
 #
@@ -17,15 +17,19 @@
 # The expensive operations that the caches are designed to short-circuit
 # are:
 #
-#   * `Magick::Image.ping(path)` — runs inside `CheesyGallery::ImageFile`'s
-#     Geometry-cache `getset` block. Exactly one call per source image
-#     on a Geometry-cache miss; zero calls on a hit.
+#   * `Vips::Image.new_from_file(path)` — runs inside
+#     `CheesyGallery::ImageFile`'s Geometry-cache `getset` block.
+#     Exactly one call per source image on a Geometry-cache miss; zero
+#     calls on a hit. The header read is cheap but non-trivial (libvips
+#     opens the file and parses the JPEG marker chain).
 #
-#   * `Magick::ImageList.new(path)` — the first line of
-#     `BaseImageFile#copy_file`, which is reached only when Layer A
-#     (mtimes/dest existence) and Layer B (Render cache) both miss.
-#     Exactly one call per variant on a Layer-B miss; zero calls on
-#     a hit.
+#   * `Vips::Image.thumbnail(path, ...)` — the fused decode + resize
+#     used by every subclass's `process_and_write`. Reached only when
+#     Layer A (mtimes/dest existence) and Layer B (Render cache) both
+#     miss. Exactly one call per variant on a Layer-B miss; zero calls
+#     on a hit. Under libvips the legacy "decode" and "resize" steps
+#     are a single fused operation, so we count one `thumbnail` call
+#     where the RMagick generation counted one `Magick::ImageList.new`.
 #
 # We install spies via `and_wrap_original` so the original calls still
 # happen (we want real Jekyll output) and assert per-scenario counts.
@@ -36,7 +40,7 @@
 # calls by clearing in-memory class state without touching the on-disk
 # cache or the rendered `_site/` tree — that's the only state a fresh
 # Ruby process would actually have lost.
-# Use the smaller _gallery_two JPGs (~1000x750) to keep RMagick work
+# Use the smaller _gallery_two JPGs (~1000x750) to keep libvips work
 # cheap across the matrix of scenarios.
 CHEESY_CACHE_FIXTURE_DIR  = File.expand_path('../fixtures/test_site/_gallery_two', __dir__)
 CHEESY_CACHE_FIXTURE_JPGS = %w[Frostig-001.jpg Frostig-003.jpg].freeze
@@ -69,15 +73,15 @@ def install_spies!
     @decode_count = 0
     @ping_paths   = []
     @decode_paths = []
-    allow(Magick::Image).to receive(:ping).and_wrap_original do |orig, *args|
+    allow(Vips::Image).to receive(:new_from_file).and_wrap_original do |orig, *args, **kwargs|
       @ping_count += 1
       @ping_paths << args.first
-      orig.call(*args)
+      orig.call(*args, **kwargs)
     end
-    allow(Magick::ImageList).to receive(:new).and_wrap_original do |orig, *args|
+    allow(Vips::Image).to receive(:thumbnail).and_wrap_original do |orig, *args, **kwargs|
       @decode_count += 1
       @decode_paths << args.first
-      orig.call(*args)
+      orig.call(*args, **kwargs)
     end
   end
 
@@ -186,7 +190,7 @@ def geometry_cache_files
   # --- §3.3 scenario 2: warm second build, no source changes ---------
 
   describe 'scenario 2: warm second build, no source changes' do
-    it 'does no RMagick work at all (Layers B and C both hit)' do
+    it 'does no libvips work at all (Layers B and C both hit)' do
       build!
       simulate_cold_process!
       reset_counters!
@@ -210,7 +214,7 @@ def geometry_cache_files
   # --- §3.3 scenario 3: warm build with one new photo ----------------
 
   describe 'scenario 3: warm build with one new photo' do
-    it 'only does RMagick work for the new source' do
+    it 'only does libvips work for the new source' do
       build!
       simulate_cold_process!
       new_jpg = File.join(source_dir, '_gallery', 'zzz-new-photo.jpg')
@@ -340,7 +344,7 @@ def geometry_cache_files
         expect(File.realdirpath(realpath)).to eq(realpath)
         expect(mtime).to match(%r{\A\d{4}-\d{2}-\d{2}})
         # The geometry component is the `geometry_string` that
-        # ImageFile passes to `change_geometry!`, with the `>`
+        # ImageFile uses for cache fingerprinting, with the `>`
         # appended so we never upscale small originals.
         expect(geom).to eq('1920x1080>')
       end

spec/cheesy/generator_spec.rb

@@ -4,7 +4,7 @@
 require 'jekyll'
 require 'fileutils'
 require 'tmpdir'
-require 'rmagick'
+require 'vips'
 
 # Plugin-behaviour specs covering docs/todos.md §4: end-to-end site
 # generation, the synthetic GalleryIndex doc for index-less gallery
@@ -329,13 +329,9 @@ def write_two_gallery_fixture!
       write_two_gallery_fixture!
       build!
 
-      out = Magick::Image.ping(File.join(dest_dir, 'gallery_two', 'Frostig-001.jpg')).first
-      begin
-        expect(out.columns).to be <= 600
-        expect(out.rows).to be <= 400
-      ensure
-        out.destroy!
-      end
+      out = Vips::Image.new_from_file(File.join(dest_dir, 'gallery_two', 'Frostig-001.jpg')).autorot
+      expect(out.width).to be <= 600
+      expect(out.height).to be <= 400
     end
 
     it 'leaves rendered output at source size when below the default max_size' do
@@ -344,12 +340,8 @@ def write_two_gallery_fixture!
 
       # Shrink-only `>` policy: 1000x750 stays 1000x750 under the
       # default '1920x1080' max_size.
-      out = Magick::Image.ping(File.join(dest_dir, 'gallery_one', 'Frostig-001.jpg')).first
-      begin
-        expect([out.columns, out.rows]).to eq([1000, 750])
-      ensure
-        out.destroy!
-      end
+      out = Vips::Image.new_from_file(File.join(dest_dir, 'gallery_one', 'Frostig-001.jpg')).autorot
+      expect([out.width, out.height]).to eq([1000, 750])
     end
 
     it 'passes max_size and quality through from collection metadata to ImageFile' do

spec/fixtures/test_site/Gemfile.lock

@@ -1,9 +1,9 @@
 PATH
   remote: ../../..
   specs:
-    cheesy-gallery (1.1.1)
+    cheesy-gallery (1.2.0)
       jekyll (~> 4.4)
-      rmagick (>= 4, < 6)
+      ruby-vips (~> 2.2)
 
 GEM
   remote: https://rubygems.org/
@@ -70,20 +70,18 @@ GEM
       jekyll (>= 3.5, < 5.0)
       jekyll-feed (~> 0.9)
       jekyll-seo-tag (~> 2.1)
-    observer (0.1.2)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
-    pkg-config (1.6.5)
     public_suffix (7.0.5)
     rake (13.4.2)
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
     rexml (3.4.4)
-    rmagick (5.5.0)
-      observer (~> 0.1)
-      pkg-config (~> 1.4)
     rouge (4.7.0)
+    ruby-vips (2.3.0)
+      ffi (~> 1.12)
+      logger
     safe_yaml (1.0.5)
     sass-embedded (1.99.0)
       google-protobuf (~> 4.31)