lib/prawn/images/jpg.rb in prawn-1.0.0.rc2 vs lib/prawn/images/jpg.rb in prawn-1.0.0

@@ -8,41 +8,47 @@
 
 require 'stringio'
 
 module Prawn
   module Images
+
     # A convenience class that wraps the logic for extracting the parts
     # of a JPG image that we need to embed them in a PDF
     #
     class JPG < Image
+      # @group Extension API
+      
       attr_reader :width, :height, :bits, :channels
       attr_accessor :scaled_width, :scaled_height
-      
-      JPEG_SOF_BLOCKS = %W(\xc0 \xc1 \xc2 \xc3 \xc5 \xc6 \xc7 \xc9 \xca \xcb \xcd \xce \xcf)
-      JPEG_APP_BLOCKS = %W(\xe0 \xe1 \xe2 \xe3 \xe4 \xe5 \xe6 \xe7 \xe8 \xe9 \xea \xeb \xec \xed \xee \xef)
 
+      JPEG_SOF_BLOCKS = [0xC0, 0xC1, 0xC2, 0xC3, 0xC5, 0xC6, 0xC7, 0xC9, 0xCA, 0xCB, 0xCD, 0xCE, 0xCF]
+
+      def self.can_render?(image_blob)
+        image_blob[0, 3].unpack("C*") == [255, 216, 255]
+      end
+
       # Process a new JPG image
       #
       # <tt>:data</tt>:: A binary string of JPEG data
       #
       def initialize(data)
-        @data = data.dup
-        ruby_19 { data.force_encoding("binary") }
-        data = StringIO.new(data)
+        @data = data
+        d = StringIO.new(@data)
+        d.binmode
 
-        c_marker = "\xff" # Section marker.
-        data.read(2)   # Skip the first two bytes of JPEG identifier.
+        c_marker = 0xff # Section marker.
+        d.seek(2)    # Skip the first two bytes of JPEG identifier.
         loop do
-          marker, code, length = data.read(4).unpack('aan')
+          marker, code, length = d.read(4).unpack('CCn')
           raise "JPEG marker not found!" if marker != c_marker
 
           if JPEG_SOF_BLOCKS.include?(code)
-            @bits, @height, @width, @channels = data.read(6).unpack("CnnC")
+            @bits, @height, @width, @channels = d.read(6).unpack("CnnC")
             break
           end
 
-          buffer = data.read(length - 2)
+          d.seek(length - 2, IO::SEEK_CUR)
         end
       end
 
       # Build a PDF object representing this image in +document+, and return
       # a Reference to it.
@@ -60,24 +66,24 @@
         end
 
         obj = document.ref!(
           :Type             => :XObject,
           :Subtype          => :Image,
-          :Filter           => :DCTDecode,
           :ColorSpace       => color_space,
           :BitsPerComponent => bits,
           :Width            => width,
           :Height           => height
-        ) 
+        )
 
         # add extra decode params for CMYK images. By swapping the
         # min and max values from the default, we invert the colours. See
         # section 4.8.4 of the spec.
         if color_space == :DeviceCMYK
           obj.data[:Decode] = [ 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0 ]
         end
 
-        obj << @data
+        obj.stream << @data
+        obj.stream.filters << :DCTDecode
         obj
       end
 
     end
   end