title: AttributeError: 'numpy.ndarray' object has no attribute 'append':Image processing example
body: <p>I will first explain what I want to do. I have an image and I want to store the pixel values for a specific ROI. For that reason I implement the following loop(found in another topic of the site):</p>
  
  <pre><code>pixels = im.load() 
  
  all_pixels = []
  for x in range(SpecificWidth):
    for y in range(SpecificHeight):
      cpixel = pixels[x, y]
      all_pixels.append(cpixel)
  </code></pre>
  
  <p>However, it does not return a SpecificwidthXSpecificHeight matrix but one of length as much as the values. Because I want to keep the size of the matrix of the ROI I implement the following loop(much the same with the previous):</p>
  
  <pre><code>array=np.array(all_pixels)
  roi_pixels = np.zeros((SpecificWidth,SpecificHeight))
  
  for i in range(0,array.shape[0],width):
      c_roi_pixels=all_pixels[i]
      roi_pixels.append(c_roi_pixels)
  </code></pre>
  
  <p>And I have the error as it mentioned in the title.</p>