title: Shrink/resize an image without interpolation
body: <p>I have an image <code>F</code> of size 1044*1408, it only has 3 integer values 0, 2, and 3. </p>
  
  <p>I want to shrink it to 360*480. Now I am using <code>Z= cv2.resize(F,(480,380))</code>. But <code>Z</code> is interpolated, it has many unique values, more than just 0, 2 and 3. I can't just round up the interpolated values to the closest integer, because I will get some 1s.</p>
  
  <p><code>F</code> is read from a tif file and manipulated, it is an ndarray now. So I can't use PIL: <code>F = F.resize((new_width, new_height))</code> as <code>F</code> is not from <code>F = Image.open(*)</code>.</p>