br/>A[x2][y1]--</td>
            </tr>
            <tr>
                <th class="scene_desc" colspan="3">扫描水平方向</th>
            </tr>
            <tr>
                <td class="symbol"><img src="formula_scan.svg"/></td>
                <td>与前一个元素相加</td>
                <td class="code">A[x][y] &larr; A[x][y] + A[x-1][y]</td>
            </tr>
            <tr>
                <th class="scene_desc" colspan="3">扫描垂直方向</th>
            </tr>
            <tr>
        