encoding for filter 2

aberant · Nov 29, 2009 · 8286908 · 8286908
1 parent df2f760
commit 8286908
Show file tree

Hide file tree

Showing 2 changed files with 11 additions and 0 deletions.
diff --git a/lib/spittle/filters.rb b/lib/spittle/filters.rb
@@ -40,6 +40,9 @@ def encode( filter_type, value, index, row, last_row, record_width )
         when 1
           #left
           (value - fetch_pixel(index - record_width, row)) % 256
+        when 2
+          #up
+          (value - fetch_pixel(index, last_row)) % 256
         when 4
           #paeth
           left = fetch_pixel(index - record_width, row)

diff --git a/spec/lib/image_spec.rb b/spec/lib/image_spec.rb
@@ -37,4 +37,12 @@
     # second byte of pixel 2 - pixel 1 is 3.. etc
     image.filter_encoded_rows(1).should == [[1, 1, 2, 3, 3, 3, 3]]
   end
+
+  it "can encode the rows with filter 2" do
+    image = @builder.build( :width => 2, :height => 1, :name => "image1", :data => [0,1,2,3,4,5,6] )
+    result = image.fill_to_height(2)
+
+    # filter byte of 2
+    result.filter_encoded_rows(2).should == [[2, 1, 2, 3, 4, 5, 6], [2, 255, 254, 253, 252, 251, 250]]
+  end
 end