digits: Update docstring

digits.py

@@ -1,19 +1,21 @@
 #!/usr/bin/env python
 
 '''
-SVM and KNearest digit recognition.
+SVM, Random forest and KNearest digit recognition.
+Modified from the OpenCV example.
 
 Sample loads a dataset of handwritten digits from '../data/digits.png'.
-Then it trains a SVM and KNearest classifiers on it and evaluates
+Then it trains a Random Forest, SVM and KNearest classifiers on it and evaluates
 their accuracy.
 
 Following preprocessing is applied to the dataset:
   - Moment-based image deskew (see deskew())
- - Digit images are split into 4 10x10 cells and 16-bin
+  - Digit images are split into 4 10x10 cells and 16-bin histogram of oriented
-   histogram of oriented gradients is computed for each
+    gradients is computed for each cell
-   cell
   - Transform histograms to space with Hellinger metric (see [1] (RootSIFT))
 
+Or in the "simple setting":
+  - Only moment-based image deskew (see deskew())
 
 [1] R. Arandjelovic, A. Zisserman
     "Three things everyone should know to improve object retrieval"