fixes #433

lib/image/png.coffee

@@ -8,28 +8,28 @@ class PNGImage
     @height = @image.height
     @imgData = @image.imgData
     @obj = null
-    
+
   embed: (@document) ->
     return if @obj
-    
-    @obj = document.ref
+
+    @obj = @document.ref
       Type: 'XObject'
       Subtype: 'Image'
       BitsPerComponent: @image.bits
       Width: @width
       Height: @height
       Filter: 'FlateDecode'
-      
+
     unless @image.hasAlphaChannel
-      params = document.ref
+      params = @document.ref
         Predictor: 15
         Colors: @image.colors
         BitsPerComponent: @image.bits
         Columns: @width
-        
+
       @obj.data['DecodeParms'] = params
       params.end()
-        
+
     if @image.palette.length is 0
       @obj.data['ColorSpace'] = @image.colorSpace
     else
@@ -39,7 +39,7 @@ class PNGImage
 
       # build the color space array for the image
       @obj.data['ColorSpace'] = ['Indexed', 'DeviceRGB', (@image.palette.length / 3) - 1, palette]
-      
+
     # For PNG color types 0, 2 and 3, the transparency data is stored in
     # a dedicated PNG chunk.
     if @image.transparency.grayscale
@@ -57,21 +57,21 @@ class PNGImage
         mask.push x, x
 
       @obj.data['Mask'] = mask
-      
+
     else if @image.transparency.indexed
-      # Create a transparency SMask for the image based on the data 
+      # Create a transparency SMask for the image based on the data
       # in the PLTE and tRNS sections. See below for details on SMasks.
       @loadIndexedAlphaChannel()
-      
+
     else if @image.hasAlphaChannel
       # For PNG color types 4 and 6, the transparency data is stored as a alpha
       # channel mixed in with the main image data. Separate this data out into an
       # SMask object and store it separately in the PDF.
       @splitAlphaChannel()
-      
+
     else
       @finalize()
-      
+
   finalize: ->
     if @alphaChannel
       sMask = @document.ref
@@ -89,11 +89,11 @@ class PNGImage
 
     # add the actual image data
     @obj.end @imgData
-    
+
     # free memory
     @image = null
     @imgData = null
-    
+
   splitAlphaChannel: ->
     @image.decodePixels (pixels) =>
       colorByteSize = @image.colors * @image.bits / 8
@@ -117,7 +117,7 @@ class PNGImage
       zlib.deflate alphaChannel, (err, @alphaChannel) =>
         throw err if err
         @finalize() if ++done is 2
-        
+
   loadIndexedAlphaChannel: (fn) ->
     transparency = @image.transparency.indexed
     @image.decodePixels (pixels) =>
@@ -130,5 +130,5 @@ class PNGImage
       zlib.deflate alphaChannel, (err, @alphaChannel) =>
         throw err if err
         @finalize()
-    
+
 module.exports = PNGImage