title: Seaborn Heatmap without lines between cells
body: <p>I´m trying to create a heatmap with seaborn with a transparent colormap since an image should be displayed in the background. The heatmap creation works fine so far, however some lines between the cells are still visible even though the linewidth of the heatmap is set to 0.0.</p>
  
  <p>The code for the creation of the heatmap looks like the following:</p>
  
  <pre><code>ax = sns.heatmap(image, cmap="rocket_r", linewidths=0.0)
  ax.collections[0].set_alpha(0.5)
  </code></pre>
  
  <p>Where <code>image</code> is 64x64 numpy array. The resulting heatmap looks like this:
  <a href="https://i.stack.imgur.com/4sRoT.png" rel="nofollow noreferrer">Heatmap</a> (sorry not enough repuation for embedding pictures)</p>
  
  <p>The problem are the thin lines between the cells. Strangely they aren´t at every edge.</p>
  
  <p>Anyone knows how to get rid of those lines?</p>
  
  <p>Many Thanks</p>
  
  <hr>
  
  <p>Update 1 (Complete working example):</p>
  
  <pre><code>image = np.array([[1, 1, 2, 2], [3, 3, 3, 3], [4, 5, 4, 5], [6, 6, 6, 6]])
  ax = sns.heatmap(image, cmap="rocket_r", linewidths=0.0)
  ax.collections[0].set_alpha(0.5)
  plt.show()
  </code></pre>
  
  <p>Results is this heatmap: </p>
  
  <p><img src="https://i.stack.imgur.com/uVa5i.png" alt="this heatmap"></p>
  
  <p>Here you can see that there are thin lines between every column but there isn´t any line between the first and second row.</p>