Display the score/confidence value [(#1429)](GoogleCloudPlatform/python-docs-samples#1429)

* Display the score/confidence value

A small code addition to display the score/confidence value of a detected face above the face detection box on the output image. This is very useful to know the confidence!

* Changes applied to meet coding style requirements 

I have edited the already submitted code to meet the coding style requirements!

* Edits because white spaces

Author: peshmerge

samples/snippets/face_detection/faces.py

@@ -21,7 +21,7 @@
 # [START vision_face_detection_tutorial_imports]
 from google.cloud import vision
 from google.cloud.vision import types
-from PIL import Image, ImageDraw
+from PIL import Image, ImageDraw, ImageFont
 # [END vision_face_detection_tutorial_imports]
 
 
@@ -59,12 +59,18 @@ def highlight_faces(image, faces, output_filename):
     """
     im = Image.open(image)
     draw = ImageDraw.Draw(im)
-
+    # Sepecify the font-family and the font-size
+    font = ImageFont.truetype("arial.ttf", 25)
     for face in faces:
         box = [(vertex.x, vertex.y)
                for vertex in face.bounding_poly.vertices]
         draw.line(box + [box[0]], width=5, fill='#00ff00')
-
+        # Place the confidence value/score of the detected faces above the
+        # detection box in the output image
+        draw.text(((face.bounding_poly.vertices)[0].x,
+                   (face.bounding_poly.vertices)[0].y - 30),
+                  str(format(face.detection_confidence, '.3f')) + '%',
+                  font=font, fill='#FF0000')
     im.save(output_filename)
 # [END vision_face_detection_tutorial_process_response]