resolves #2337 honor GS_OPTIONS environment variable in RGhost optimizer (PR #2338)

7 files changed, 67 insertions, 1 deletions

diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 391285e5..eaec6e18 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -24,6 +24,7 @@ Enhancements::
 * sort using collation (asciibetical sorting) if ffi-icu gem is available on load path (#928)
 * restrict categories to ASCII letters (using transliteration) if ffi-icu gem is available on load path (#928)
 * upgrade to prawn-icon 3.1.x to add support for the Material Design Icons (`mdi`) as an available font-based icon set (PR #2334)
+* honor `GS_OPTIONS` environment variable for supplying additional parameters to command called by RGhost optimizer (#2337)
 
 Improvements::
 
diff --git a/docs/modules/ROOT/pages/optimize-pdf.adoc b/docs/modules/ROOT/pages/optimize-pdf.adoc
index 90abc678..3579073c 100644
--- a/docs/modules/ROOT/pages/optimize-pdf.adoc
+++ b/docs/modules/ROOT/pages/optimize-pdf.adoc
@@ -1,5 +1,6 @@
 = Optimize the PDF
-:url-hexapdf: https://hexapdf.gettalong.org/
+:url-hexapdf: https://hexapdf.gettalong.org
+:url-gs-pdfwrite: https://ghostscript.com/doc/current/VectorDevices.htm#PDFWRITE
 
 By default, Asciidoctor PDF does not optimize the PDF it generates or compresses its streams.
 This page covers several approaches you can take to optimize your PDF.
@@ -61,6 +62,12 @@ Here's how we set the `GS` environment variable using PowerShell in CI:
 
  $ echo "$(& where.exe /R 'C:\Program Files\gs' gswin64c.exe)" | Out-File -FilePath $env:GS -Encoding utf8 -Append
 
+If you want to pass additional {url-gs-pdfwrite}[command-line arguments to Ghostscript], you can use the `GS_OPTIONS` environment variable.
+The optimizer expects the value to be a space-separated list of arguments (e.g., `-dBlackText`).
+For example, here's how you would get the optimizer to generate a grayscale PDF with vectorized text:
+
+ $ GS_OPTIONS='-sColorConversionStrategy=Gray -dNoOutputFonts' asciidoctor-pdf -a optimize filename.adoc
+
 In addition to optimizing the PDF file, you can also configure the optimizer to convert the document from standard PDF to PDF/A or PDF/X.
 To do so, you can pass one of the following compliance keywords in the value of the optimize attribute: `PDF/A`, `PDF/A-1`, `PDF/A-2`, `PDF/A-3`, `PDF/X`, `PDF/X-1`, or `PDF/X-3`.
 
diff --git a/lib/asciidoctor/pdf/optimizer/rghost.rb b/lib/asciidoctor/pdf/optimizer/rghost.rb
index e86366e1..feea3efe 100644
--- a/lib/asciidoctor/pdf/optimizer/rghost.rb
+++ b/lib/asciidoctor/pdf/optimizer/rghost.rb
@@ -29,6 +29,8 @@ end)
 module Asciidoctor
   module PDF
     class Optimizer::RGhost < Optimizer::Base
+      DEFAULT_PARAMS = %w(gs -dNOPAUSE -dBATCH -dQUIET -dNOPAGEPROMPT)
+
       # see https://www.ghostscript.com/doc/current/VectorDevices.htm#PSPDF_IN for details
       (QUALITY_NAMES = {
         'default' => :default,
@@ -43,6 +45,11 @@ module Asciidoctor
         if (gs_path = ::ENV['GS'])
           ::RGhost::Config::GS[:path] = gs_path
         end
+        default_params = DEFAULT_PARAMS.drop 0
+        if (user_params = ::ENV['GS_OPTIONS'])
+          (default_params += user_params.split).uniq!
+        end
+        ::RGhost::Config::GS[:default_params] = default_params
       end
 
       def optimize_file target
diff --git a/spec/fixtures/with-color.adoc b/spec/fixtures/with-color.adoc
new file mode 100644
index 00000000..85594ed3
--- /dev/null
+++ b/spec/fixtures/with-color.adoc
@@ -0,0 +1,16 @@
+= Document With Color
+:source-highlighter: rouge
+
+This document has color.
+
+image::square.svg[]
+
+.Create a basic PDF document using Prawn
+[,ruby]
+----
+require 'prawn'
+
+Prawn::Document.generate 'example.pdf' do
+  text 'Hello, World!'
+end
+----
diff --git a/spec/optimizer_spec.rb b/spec/optimizer_spec.rb
index 479426b4..e395bf16 100644
--- a/spec/optimizer_spec.rb
+++ b/spec/optimizer_spec.rb
@@ -151,6 +151,29 @@ describe 'Asciidoctor::PDF::Optimizer', if: (RSpec::ExampleGroupHelpers.gem_avai
     (expect pdf_info[:Producer]).to include 'Ghostscript'
   end
 
+  it 'should append parameter specified in GS_OPTIONS environment variable', cli: true, visual: true do
+    env = { 'GS_OPTIONS' => '-dNoOutputFonts' }
+    out, err, res = run_command asciidoctor_pdf_bin, '-a', 'optimize', '-o', (to_file = output_file 'optimizer-gs-options-single.pdf'), (example_file 'basic-example.adoc'), env: env
+    (expect res.exitstatus).to be 0
+    (expect out).to be_empty
+    (expect err).to be_empty
+    pdf = TextInspector.analyze Pathname.new to_file
+    (expect pdf.text).to be_empty
+  end
+
+  it 'should append all parameters specified in GS_OPTIONS environment variable', cli: true, visual: true do
+    env = { 'GS_OPTIONS' => '-sColorConversionStrategy=Gray -dBlackText' }
+    out, err, res = run_command asciidoctor_pdf_bin, '-a', 'optimize', '-o', (to_file = output_file 'optimizer-gs-options-multiple.pdf'), (fixture_file 'with-color.adoc'), env: env
+    (expect res.exitstatus).to be 0
+    (expect out).to be_empty
+    (expect err).to be_empty
+    pdf = TextInspector.analyze Pathname.new to_file
+    (expect pdf.text.map {|it| it[:font_color] }.uniq).to eql [nil]
+    rects = (RectInspector.analyze Pathname.new to_file).rectangles
+    (expect rects).to have_size 1
+    (expect rects[0][:fill_color]).to eql '818181'
+  end
+
   it 'should not crash if quality passed to asciidoctor-pdf-optimize CLI is not recognized', cli: true do
     input_file = Pathname.new example_file 'basic-example.adoc'
     to_file = to_pdf_file input_file, 'optimizer-cli-fallback-quality.pdf'
diff --git a/spec/spec_helper/inspectors/rect.rb b/spec/spec_helper/inspectors/rect.rb
index 0b097cf9..a29f21d8 100644
--- a/spec/spec_helper/inspectors/rect.rb
+++ b/spec/spec_helper/inspectors/rect.rb
@@ -51,4 +51,15 @@ class RectInspector < PDF::Inspector
   def set_color_for_stroking_and_special *params
     @stroke_color = params.size == 4 ? params.map {|it| it * 100 } : params.map {|it| sprintf '%02X', (it.to_f * 255).round }.join
   end
+
+  # rg
+  def set_rgb_color_for_nonstroking *params
+    @fill_color = params.size == 4 ? params.map {|it| it * 100 } : params.map {|it| sprintf '%02X', (it.to_f * 255).round }.join
+  end
+
+  # g
+  def set_gray_for_nonstroking *params
+    params *= 3
+    @fill_color = params.size == 4 ? params.map {|it| it * 100 } : params.map {|it| sprintf '%02X', (it.to_f * 255).round }.join
+  end
 end
diff --git a/spec/spec_helper/inspectors/text.rb b/spec/spec_helper/inspectors/text.rb
index a3204fc8..94d2bc0c 100644
--- a/spec/spec_helper/inspectors/text.rb
+++ b/spec/spec_helper/inspectors/text.rb
@@ -118,6 +118,7 @@ class TextInspector < PDF::Inspector
       @pages[-1][:text] << accum
       @cursor = nil
     else
+      @text << { string: '', width: 0 } if @text.empty?
       (accum = @text[-1])[:string] += string
       accum[:width] += text_width
     end