Merge pull request #42 from wildlyinaccurate/maintain-source-interlace

Maintain source image interlace mode

features/image-generation.feature

@@ -38,6 +38,18 @@ Feature: Responsive image generation
     And the file "assets/resized/subdir/test-100.png" should exist
     And the file "_site/assets/resized/subdir/test-100.png" should exist
 
+  Scenario: Honouring source image interlace mode
+    Given I have a responsive_image configuration with:
+      """
+        template: _includes/responsive-image.html
+        sizes:
+          - width: 100
+      """
+
+    And I have a file "index.html" with "{% responsive_image path: assets/progressive.jpeg %}"
+    When I run Jekyll
+    Then the image "assets/resized/progressive-100x50.jpeg" should be interlaced
+
   Scenario: Honouring Jekyll 'source' configuration
     Given I have copied my site to "my-site-copy/src"
     And I have a configuration with:

features/step_definitions/jekyll_steps.rb

@@ -59,6 +59,12 @@ Then /^the image "(.+)" should have the dimensions "(\d+)x(\d+)"$/ do |path, wid
   img.destroy!
 end
 
+Then /^the image "(.+)" should be interlaced$/ do |path|
+  img = Magick::Image::read(path).first
+  assert_equal Magick::JPEGInterlace, img.interlace
+  img.destroy!
+end
+
 def write_file(path, contents)
   File.open(path, 'w') do |f|
     f.write(contents)

lib/jekyll-responsive-image/resize_handler.rb

@@ -30,6 +30,7 @@ module Jekyll
 
           i = img.scale(ratio)
           i.write(site_source_filepath) do |f|
+            f.interlace = i.interlace
             f.quality = size['quality'] || config['default_quality']
           end