Update README.md

README.md

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-hmap
+Hmap
 ====
 
-Image histogram mapping
+An image histogram remapping script written in Python 2.7 by Anthony Kesich and Ross Goodwin. Changes source image so that source image's histogram matches target image's histogram. Requires PIL/Pillow:
+
+    $ sudo pip install Pillow
+
+To run Hmap, cd into the directory where the hmap.py (for black and white images) or hmap_c.py (for color images) is located. Ensure source and target images have the same height and width dimensions (in pixels), and place them in the directory. Run the script with 2 additional arguments (source and target image files) as shown in the following example.
+
+Example:
+
+    $ sudo python hmap\_c.py source\_image.jpg target\_image.jpg