Image Smoother

Given a 2D integer matrix M representing the gray scale of an image, you need to design a smoother to make the gray scale of each cell becomes the average gray scale (rounding down) of all the 8 surrounding cells and itself. If a cell has less than 8 surrounding cells, then use as many as you can.

Example 1:

Input:
[[1,1,1],
 [1,0,1],
 [1,1,1]]
Output:
[[0, 0, 0],
 [0, 0, 0],
 [0, 0, 0]]
Explanation:
For the point (0,0), (0,2), (2,0), (2,2): floor(3/4) = floor(0.75) = 0
For the point (0,1), (1,0), (1,2), (2,1): floor(5/6) = floor(0.83333333) = 0
For the point (1,1): floor(8/9) = floor(0.88888889) = 0

Note:

1. The value in the given matrix is in the range of [0, 255].
2. The length and width of the given matrix are in the range of [1, 150].

 1 class Solution {
 2     public int[][] imageSmoother(int[][] M) {
 3         int m = M.length, n = M[0].length;
 4         int result[][] = new int[m][n];
 5         
 6         for (int i = 0; i < m; i++) {
 7             for (int j = 0; j < n; j++) {
 8                 int[] surroundings = countSurroundings(M, i, j);
 9                 result[i][j] = surroundings[0] / surroundings[1];
10             }
11         }
12         
13         return result;
14     }
15     
16     private int[] countSurroundings(int[][] M, int i, int j) {
17         int result[] = {0, 0}; // surroundingCount, surroundingNumber
18         for (int ii = i - 1; ii <= i + 1; ii++) {
19             for (int jj = j - 1; jj <= j + 1; jj++) {
20                 if (ii < 0 || jj < 0 || ii >= M.length || jj >= M[0].length) {
21                     continue;
22                 } else {
23                     result[1] += 1;
24                     result[0] += M[ii][jj];
25                 }
26             }
27         }
28         
29         return result;
30     }
31 }