Merge pull request #24 from Rubikan/master

added the possibility to use imagemagick's -alpha option

Author: jonmagic

lib/grim/image_magick_processor.rb

@@ -9,7 +9,7 @@ class ImageMagickProcessor
     def initialize(options={})
       @imagemagick_path = options[:imagemagick_path] || DefaultImagemagickPath
       @ghostscript_path = options[:ghostscript_path] || DefaultGhostScriptPath
-      @original_path        = ENV['PATH']
+      @original_path    = ENV['PATH']
     end
 
     def count(path)
@@ -21,14 +21,25 @@ def count(path)
     end
 
     def save(pdf, index, path, options)
-      width   = options.fetch(:width,   Grim::WIDTH)
-      density = options.fetch(:density, Grim::DENSITY)
-      quality = options.fetch(:quality, Grim::QUALITY)
+      width      = options.fetch(:width,   Grim::WIDTH)
+      density    = options.fetch(:density, Grim::DENSITY)
+      quality    = options.fetch(:quality, Grim::QUALITY)
       colorspace = options.fetch(:colorspace, Grim::COLORSPACE)
-      command = [@imagemagick_path, "-resize", width.to_s, "-antialias", "-render",
-        "-quality", quality.to_s, "-colorspace", colorspace,
-        "-interlace", "none", "-density", density.to_s,
-        "#{Shellwords.shellescape(pdf.path)}[#{index}]", path]
+      alpha      = options[:alpha]
+
+      command = []
+      command << @imagemagick_path
+      command << "-resize #{width}"
+      command << "-alpha #{alpha}" if alpha
+      command << "-antialias"
+      command << "-render"
+      command << "-quality #{quality}"
+      command << "-colorspace #{colorspace}"
+      command << "-interlace none"
+      command << "-density #{density}"
+      command << "#{Shellwords.shellescape(pdf.path)}[#{index}]"
+      command << path
+
       command.unshift("PATH=#{File.dirname(@ghostscript_path)}:#{ENV['PATH']}") if @ghostscript_path && @ghostscript_path != DefaultGhostScriptPath
 
       result = `#{command.join(' ')}`

spec/fixtures/remove_alpha.pdf

@@ -112,4 +112,20 @@
       expect(file1_size).to_not eq(file2_size)
     end
   end
+  
+  describe "#save with alpha option" do
+    before(:each) do
+      @path1 = tmp_path("to_png_spec-1.png")
+      @path2 = tmp_path("to_png_spec-2.png")
+      @pdf  = Grim::Pdf.new(fixture_path("remove_alpha.pdf"))
+    end
+    
+    it "should use alpha" do
+      Grim::ImageMagickProcessor.new.save(@pdf, 0, @path1, {:alpha => 'Set'})
+      Grim::ImageMagickProcessor.new.save(@pdf, 0, @path2, {:alpha => 'Remove'})
+
+      expect(`convert #{@path1} -verbose info:`.include?("alpha: 8-bit")).to be(true)
+      expect(`convert #{@path2} -verbose info:`.include?("alpha: 1-bit")).to be(true)
+    end
+  end
 end