some small fixes

Steganography/compare_two_images.py

@@ -0,0 +1,30 @@
+#!/usr/bin/env python
+
+__author__='bt3gl'
+'''
+Compare two aligned images of the same size.
+
+Usage: python compare.py first-image second-image
+'''
+
+import sys
+
+from scipy.misc import imread, imsave
+
+
+def compare_images(img1, img2):
+    diff = img1 + img2  
+    imsave('sum.png', diff)	
+    diff = img1 - img2  
+    imsave('diff.png', diff)
+
+
+
+def main():
+    file1, file2 = sys.argv[1:1+2]
+    img1 = imread(file1).astype(float)
+    img2 = imread(file2).astype(float)
+    compare_images(img1, img2)
+
+if __name__ == "__main__":
+    main()