Making the random seeded pixel values a bit protected from infinite loopes.

image_utils.rb

@@ -6,13 +6,18 @@ class ImageUtils
 
   @@password   = ""
   @@message    = ""
+  @@salt       = 0
 
-  @@hash = nil
+  @@imagickImg = nil
 
   @@width      = 0
   @@height     = 0
 
-  @@pixel_arr = []
+  @@pixel_arr  = nil
+
+  @@hash       = nil
+
+  @@rng        = nil
 
   def initialize(pass, msg, uri)
     @@password = pass
@@ -26,12 +31,12 @@ class ImageUtils
 
     @@pixel_arr = @@magickImg.get_pixels(0, 0, @@width, @@height)
 
-    if msg.length > 1024 then
-      puts "Maximum length exceeded.  Exiting."
-      exit
-    end
+    @@hash = self.generateHash
 
-    self.generateHash
+    # convert hex string into an int to store for making the lookup table
+    @@rng = Random.new(@@hash.to_i(16))
+
+    puts self.getLookupTable.inspect
   end
 
   def getPixel(x, y)
@@ -59,41 +64,53 @@ class ImageUtils
   def generateHash
     pass_h = Digest::SHA512.hexdigest(@@password)
 
-    @@hash = Digest::SHA512.hexdigest(pass_h + @@salt.to_s)
+    return Digest::SHA512.hexdigest(pass_h + @@salt.to_s)
   end
 
-  def generateLookupTable
+  def getBits(o)
+    msg_bytes = o.unpack("c*")
+
+    msg_bits = 0
+
+    for b in msg_bytes
+      msg_bits = (msg_bits << 8) | b
+    end
+
+    return msg_bits
+  end
+
+  def getLookupTable
     tbl = []
 
-    hash_bits = @@pixelImg.getBits(@@hash)
-    msg_bits = @@pixelImg.getBits(@@message)
+    # track hash classes.  if too many occur during the interval, abaondon 
+    # encoding.
+    clashes = 0
+    clash_limit = 100
 
-    # gross, but pad in the 24 bits that will become the msg length
-    # and padding bits...
-    msg_bits = msg_bits << 24
+    msg_bits = self.getBits(@@message)
  	
     while msg_bits > 0 do
       loc = nil
 
       loop do
-        x = (hash_bits.to_i % @@pixelImg.getSize[:width])
-        y = (hash_bits.to_i % @@pixelImg.getSize[:height])
+        x = @@rng.rand(0..@@width)
+        y = @@rng.rand(0..@@height)
 
         loc = {"x": x, "y": y}
+        if !tbl.include?(loc) then
+          clashes = 0
+        else
+          clashes = clashes + 1
+        end
 
-      break if !tbl.include?(loc)
-        hash_bits = hash_bits >> 1
-
-        if hash_bits <= 0 then
-          puts
-          puts "wow too much data"
-          puts "leftover bits: " + msg_bits.to_s(36)
+        if clashes < clash_limit then
+          break
+        else
+          puts "wow clashed so much sorry for breaking"
           exit
         end
       end
 
-      hash_bits = hash_bits >> 1
-
       tbl.push(loc)
 
       msg_bits = msg_bits >> 6