title: ValueError buffer source array is read-only
body: <p>I'm using this code to extract GLCM features for a certain image but it gives me a value error</p>
  <p><strong>Code:</strong></p>
  <pre class="lang-py prettyprint-override"><code>from PIL import Image
  from skimage.feature import greycomatrix, greycoprops
  fname = 'trial.jpg'
  img = Image.open(fname).convert(&quot;L&quot;)
  img = img.resize((224, 224))
  test_glcm = greycomatrix(img, [1], [np.pi/2], 256, symmetric=True, normed=True)
  </code></pre>
  <p><strong>Error:</strong></p>
  <blockquote>
  <p>ValueError buffer source array is read-only</p>
  </blockquote>
  <p>Does anyone knows what that means, or what may be the problem in the code?</p>