Merge pull request #29 from jonmagic/logging

Add Grim.logger

README.md

@@ -86,6 +86,19 @@ pdf[0].save('/path/to/image.png', {
 })
 ```
 
+Grim has limited logging abilities. The default logger is `Grim::NullLogger` but you can also set your own logger.
+
+```ruby
+require "logger"
+Grim.logger = Logger.new($stdout).tap { |logger| logger.progname = 'Grim' }
+Grim.processor = Grim::ImageMagickProcessor.new({:ghostscript_path => "/path/to/bin/gs"})
+pdf = Grim.reap("/path/to/pdf")
+pdf[3].save('/path/to/image.png')
+# D, [2016-06-09T22:43:07.046532 #69344] DEBUG -- grim: Running imagemagick command
+# D, [2016-06-09T22:43:07.046626 #69344] DEBUG -- grim: PATH=/path/to/bin:/usr/local/bin:/usr/bin
+# D, [2016-06-09T22:43:07.046787 #69344] DEBUG -- grim: convert -resize 1024 -antialias -render -quality 90 -colorspace RGB -interlace none -density 300 /path/to/pdf /path/to/image.png
+```
+
 ## Reference
 
 * [jonmagic.com: Grim](http://jonmagic.com/blog/archives/2011/09/06/grim/)

lib/grim.rb

@@ -50,11 +50,26 @@ class UnprocessablePage < Grim::Exception
   def self.reap(path)
     Grim::Pdf.new(path)
   end
+
+  # Set a Logger compatible logger for Grim.
+  #
+  # logger - Object with same interface as Logger.new
+  def self.logger=(logger)
+    @logger = logger
+  end
+
+  # Logger to use internally. Defaults to Grim::NullLogger.
+  #
+  # Returns a Logger compatible logger.
+  def self.logger
+    @logger ||= Grim::NullLogger.new
+  end
 end
 
 require 'grim/pdf'
 require 'grim/page'
 require 'grim/image_magick_processor'
 require 'grim/multi_processor'
+require 'grim/null_logger'
 
-Grim.processor = Grim::ImageMagickProcessor.new
+Grim.processor = Grim::ImageMagickProcessor.new

lib/grim/image_magick_processor.rb

@@ -48,7 +48,13 @@ def save(pdf, index, path, options)
         command_env['PATH'] = "#{File.dirname(@ghostscript_path)}#{File::PATH_SEPARATOR}#{ENV['PATH']}"
       end
 
-      result, status = Open3.capture2e(command_env, command.join(' '))
+      Grim.logger.debug { "Running imagemagick command" }
+      if command_env.any?
+        Grim.logger.debug { command_env.map {|k,v| "#{k}=#{v}" }.join(" ") }
+      end
+      Grim.logger.debug { command.join(" ") }
+
+      result, status = Open3.capture2e(command_env, command.join(" "))
 
       status.success? || raise(UnprocessablePage, result)
     end

lib/grim/null_logger.rb

@@ -0,0 +1,9 @@
+require "logger"
+
+module Grim
+  class NullLogger
+    def initialize(*args); end
+    def debug(*args); end
+    def info(*args); end
+  end
+end

lib/grim/page.rb

@@ -50,7 +50,10 @@ def save(path, options={})
     # Returns a String.
     #
     def text
-      `#{[@pdftotext_path, "-enc", "UTF-8", "-f", @number, "-l", @number, Shellwords.escape(@pdf.path), "-"].join(' ')}`
+      command = [@pdftotext_path, "-enc", "UTF-8", "-f", @number, "-l", @number, Shellwords.escape(@pdf.path), "-"].join(' ')
+      Grim.logger.debug { "Running pdftotext command" }
+      Grim.logger.debug { command }
+      `#{command}`
     end
   end
 end

spec/lib/grim/null_logger_spec.rb

@@ -0,0 +1,11 @@
+require 'spec_helper'
+require "stringio"
+
+describe Grim::NullLogger do
+  it "acts like Logger but doesn't log anything" do
+    io = StringIO.new
+    logger = Grim::NullLogger.new(io)
+    logger.debug "hello world"
+    expect(io.string).to eq("")
+  end
+end

spec/lib/grim_spec.rb

@@ -26,9 +26,27 @@
     expect(Grim::COLORSPACE).to eq('RGB')
   end
 
-  describe "#reap" do
+  describe ".reap" do
     it "should return an instance of Grim::Pdf" do
       expect(Grim.reap(fixture_path("smoker.pdf")).class).to eq(Grim::Pdf)
     end
   end
+
+  describe ".logger=" do
+    it "sets Grim.logger" do
+      original_logger = Grim.logger
+      begin
+        Grim.logger = "foo"
+        expect(Grim.logger).to eq("foo")
+      ensure
+        Grim.logger = original_logger
+      end
+    end
+  end
+
+  describe ".logger" do
+    it "returns a Grim::NullLogger by default" do
+      expect(Grim.logger).to be_instance_of(Grim::NullLogger)
+    end
+  end
 end