title: opencv assertion failed error while computing HOG feature of an image in python
body: <p>I want to computer HOG feature of an image using opencv hog.compute(image) function in python. But it gave me this error </p>
  
  <blockquote>
    <p>"OpenCV Error: Assertion failed (0 &lt;= _rowRange.start &amp;&amp;
    _rowRange.start &lt;= _rowRange.end &amp;&amp; _rowRange.end &lt;= m.rows) in Mat, file /home/dipdeb/opencv-3.1.0/modules/core/src/matrix.cpp, line 469
    <strong>* Error in `python': free(): invalid next size (normal): 0x0000000002b319d0 *</strong>"</p>
  </blockquote>
  
  <p>here is my code </p>
  
  <pre><code>import cv2
  hog = cv2.HOGDescriptor()
  im = cv2.imread("35.jpg")
  h = hog.compute(im)
  </code></pre>