From c9417bddd0680a4942a05914f40c3853a6a74e38 Mon Sep 17 00:00:00 2001
From: cedricbonhomme <devnull@localhost>
Date: Tue, 5 Oct 2010 10:52:02 +0200
Subject: [PATCH] Improvements (speed) by Christophe.

---
 lsb-s.py               | 35 ++++++++++++++++++++++++++++++++++-
 steganalysis-parity.py |  8 ++++----
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/lsb-s.py b/lsb-s.py
index 65f9d8a..92b0d76 100755
--- a/lsb-s.py
+++ b/lsb-s.py
@@ -24,7 +24,6 @@ def hide(img, message):
 
     npixels = width * height
     if len(message_bits) > npixels * 3:
-        print """Too long message (%s > %s).""" % (len(message_bits), npixels * 3)
         return """Too long message (%s > %s).""" % (len(message_bits), npixels * 3)
 
     for row in range(height):
@@ -48,6 +47,40 @@ def hide(img, message):
     return encoded
 
 def reveal(img):
+    """
+    Find a message in an image
+    (with the LSB technique).
+    """
+    width, height = img.size
+    buff, count = 0, 0
+    bitab = []
+    for row in range(height):
+        for col in range(width):
+            r, g, b = img.getpixel((col, row))
+
+            buff += (r&1)<<(7-count)
+            count += 1
+            if count == 8:
+                bitab.append(chr(buff))
+                buff, count = 0, 0
+
+            buff += (g&1)<<(7-count)
+            count += 1
+            if count == 8:
+                bitab.append(chr(buff))
+                buff, count = 0, 0
+
+            buff += (b&1)<<(7-count)
+            count += 1
+            if count == 8:
+                bitab.append(chr(buff))
+                buff, count = 0, 0
+
+            if len(bitab) > 0 and bitab[-1] == chr(126):
+                return "".join(bitab)[:-1]
+    return ""
+
+def reveal_slow(img):
     """
     Find a message in an image
     (with the LSB technique).
diff --git a/steganalysis-parity.py b/steganalysis-parity.py
index 9e70a3b..48fb7ee 100644
--- a/steganalysis-parity.py
+++ b/steganalysis-parity.py
@@ -34,10 +34,10 @@ def steganalyse(img):
 
 if __name__ == '__main__':
     # Point of entry in execution mode
-    original_image_file = "./pictures/montenach.png"
-    encoded_image_file = "./pictures/montenach_enc.png"
-    original_image_file_steganalysed = "./pictures/montenach_steganalysed.png"
-    encoded_image_file_steganalysed = "./pictures/montenach_enc_steganalysed.png"
+    original_image_file = "./pictures/free.png"
+    encoded_image_file = "./pictures/free_enc.png"
+    original_image_file_steganalysed = "./pictures/free_steganalysed.png"
+    encoded_image_file_steganalysed = "./pictures/free_enc_steganalysed.png"
 
     img_original_image_file = Image.open(original_image_file)
     img_encoded_image_file = Image.open(encoded_image_file)