title: cv2.threshold() error (-210)
body: <p>I'm new to Python. </p>
  
  <p>I want to define text rotation with help of Fourier transformation.</p>
  
  <pre><code>import cv2
  import numpy as np
  import matplotlib.pyplot as plot
  
  img = cv2.imread ('Text_rot.bmp', cv2.CV_LOAD_IMAGE_GRAYSCALE)
  afterFourier =  np.log (np.abs(np.fft.fft2 (img)))
  ret1, th1 = cv2.threshold (afterFourier, 127, 255, cv2.THRESH_BINARY)
  </code></pre>
  
  <p>But this code fails with:</p>
  
  <pre><code>ret1, th1 = cv2.threshold (afterFourier, 127, 255, cv2.THRESH_BINARY)
  error: ..\..\..\src\opencv\modules\imgproc\src\thresh.cpp:783: error: (-210) 
  </code></pre>
  
  <p>Why does that cause a "-210" error?</p>