
    pixel buffer are part of the <em>lower</em> bitmap row.</p>

    <p>In all cases, one can see the pitch as the byte increment needed to
    skip to the <em>next lower scanline</em> in a given bitmap buffer.</p>

    <center>
    <table>
    <tr>
      <td>
        <img src="up_flow.png"
             height=261 width=275
             alt="negative 'pitch'">
      </td>
      <td>
        <img src="down_flow.png"
             height=263 width=273
             alt="positive 'pitch'">
      </td>
    </tr>