661. 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].

class Solution {
    public int[][] imageSmoother(int[][] M) {
         int[][] ave = new int[M.length][M[0].length];

        for (int i = 0; i < M.length; i++) {
            for (int j = 0; j < M[i].length; j++) {
                int count =0;
                if(j>0){
                    ave[i][j]+=M[i][j-1];
                    count++;
                }

                if(j<M[i].length-1){
                    ave[i][j]+=M[i][j+1];
                    count++;
                }

                if(i>0){
                    ave[i][j]+=M[i-1][j];
                    count++;
                    if(j>0){
                        ave[i][j]+=M[i-1][j-1];
                        count++;
                    }

                    if(j<M[i].length-1){
                        ave[i][j]+=M[i-1][j+1];
                        count++;
                    }
                }

                if(i<M.length-1){
                    ave[i][j]+=M[i+1][j];
                    count++;
                    if(j>0){
                        ave[i][j]+=M[i+1][j-1];
                        count++;
                    }

                    if(j<M[i].length-1){
                        ave[i][j]+=M[i+1][j+1];
                        count++;
                    }
                }

                ave[i][j]+=M[i][j];
                count++;
                ave[i][j]/=count;
            }
        }

        return ave;
    }
}