New programs implemented

* README.md: Corresponding introductions added
* display.py: Optimized in argument parsing
* gen_encoding.py: Optimized
* display_faces.py: Created for putting rectangles on faces
* paint_stuff.py: Allow users to paint green rectangles on pictures

Here are why and how to optimize argument parsing in Python:
As we know, we load a number of modules to in order to simplify the
procedure, but loading process is time-consuming. But Python allows
us to import modules whenever we want. Therefore I let the program
parse the arguments first before loading other large modules, and this
is a time-saving solution for invalid command line argument.

Just a note, though TL;DR

README.md

@@ -28,3 +28,5 @@ $ pip3 install face_recognition	# This installs dlib as its dependency
 * **mirror\_facedetect.py** to detect faces in the webcam
 * **face\_ident.py** to identify the actual person from their faces
 * **gen\_encoding.py** to generate `.face` files from images
+* **display\_faces.py** to put rectangles on the faces of a picture
+* **paint\_stuff.py** to draw rectangles by mouse on a custom background image

display.py

@@ -1,10 +1,15 @@
 #!/usr/bin/env python3
 import sys
+
+argc=len(sys.argv)
+
+if argc<2:
+    print("usage: %s image_file" % sys.argv[0])
+    exit(-1)
+
 import cv2
 import numpy
 
-assert(len(sys.argv)>=2)
-
 # Load the image file into an ndarray
 image=cv2.imread(sys.argv[1],cv2.IMREAD_UNCHANGED);
 

display_faces.py

@@ -0,0 +1,22 @@
+#!/usr/bin/env python3
+import sys
+
+argc=len(sys.argv)
+
+if argc<2:
+    print("usage: %s image_file" % sys.argv[0])
+    exit(-1)
+
+import face_recognition as fr
+import numpy as np
+import cv2
+
+image=fr.load_image_file(sys.argv[1])   # This is for face detection
+cvimg=cv2.imread(sys.argv[1],cv2.IMREAD_UNCHANGED)
+faces=fr.face_locations(image)
+
+for top,right,bottom,left in faces:
+    cvimg=cv2.rectangle(cvimg,(left,top),(right,bottom),(0,0xFF,0),3)
+
+cv2.imshow("Results from face detector",cvimg)
+cv2.waitKey(0)

gen_encoding.py

@@ -8,10 +8,6 @@
     print("usage: %s input_file [output_file]" % sys.argv[0])
     exit(-1)
 
-import numpy as np
-import face_recognition as fr
-import csv
-
 input_filename=sys.argv[1]
 output_filename=""
 if argc>=3:
@@ -22,6 +18,10 @@
     output_filename='.'.join(parts)
 print("output data to `%s'" % output_filename)
 
+import numpy as np
+import face_recognition as fr
+import csv
+
 image=fr.load_image_file(input_filename)
 encoding=fr.face_encodings(image)[0]
 # Now write the data to the output file

paint_stuff.py

@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+import sys
+
+argc=len(sys.argv)
+
+if argc<2:
+    print("usage: %s background_image" % sys.argv[0])
+    exit(-1)
+
+img_fname=sys.argv[1]
+
+import cv2
+import numpy as np
+
+x0=0
+y0=0
+flag=False
+
+img=cv2.imread(img_fname,cv2.IMREAD_UNCHANGED)
+
+win="~Put some rectangles~"
+
+def mouse_handler(event,x,y,flags,param):
+    global x0,y0,flag
+    if event==cv2.EVENT_LBUTTONDOWN:
+        print("Start drawing")
+        flag=True
+        x0=x
+        y0=y
+    elif event==cv2.EVENT_MOUSEMOVE:
+        if flag:
+            tmp=np.array(img,copy=True)  # Make a copy from it
+            cv2.rectangle(tmp,(x0,y0),(x,y),(0,0xFF,0),3)
+            cv2.imshow(win,tmp)
+    elif event==cv2.EVENT_LBUTTONUP:
+        flag=False
+        print("Rectangle between (%d,%d) and (%d,%d)" % (x0,y0,x,y))
+        cv2.rectangle(img,(x0,y0),(x,y),(0,0xFF,0),3)
+        cv2.imshow(win,img)
+
+cv2.namedWindow(win)
+cv2.setMouseCallback(win,mouse_handler)
+cv2.imshow(win,img)
+cv2.waitKey(0)