title: opencv-python basic ORB feature detection gives me error -215 in function cv::drawKeypoints
body: <p>this is the basic code from opencv-python documentation:</p>
  
  <pre><code>import numpy as np
  import cv2
  from matplotlib import pyplot as plt
  
  img = cv2.imread('simple.jpg',0)
  
  # Initiate STAR detector
  orb = cv2.ORB()
  
  # find the keypoints with ORB
  kp = orb.detect(img,None)
  
  # compute the descriptors with ORB
  kp, des = orb.compute(img, kp)
  
  # draw only keypoints location,not size and orientation
  img2 = cv2.drawKeypoints(img,kp,color=(0,255,0), flags=0)
  plt.imshow(img2),plt.show()
  </code></pre>
  
  <p>and it gives me this error:</p>
  
  <pre><code>Traceback (most recent call last):
  File "C:\Python27\test.py", line 18, in &lt;module&gt;
  img2 = cv2.drawKeypoints(img,kp,color=(0,255,0), flags=0)
  error: ..\..\..\..\opencv\modules\features2d\src\draw.cpp:115: error:       (-215) !outImage.empty() in function cv::drawKeypoints
  </code></pre>
  
  <p>i have to mention this error happens in opencv-PYTHON, can you help me out please? struggling really to make it work</p>