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) = 0For the point (0,1), (1,0), (1,2), (2,1): floor(5/6) = floor(0.83333333) = 0For 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].

思路：

实现类似卷积的效果。

vector
     
      
       > imageSmoother(vector
       
        
         >& M){    vector
         
          
           > ret( M ); int sum = 0; int rowNum = M.size(); int colNum = M[0].size(); int cnt = 0; for( int i = 0; i < rowNum; i++ ) { for( int j = 0; j < colNum; j++ ) { sum = 0; cnt = 0; for( int k = i-1; k <= i+1; k++ ) { for( int p = j - 1; p <= j+1; p++ ) { if( k < 0 || p < 0 || k >= rowNum || p >= colNum ) { continue; } sum += M[k][p]; cnt++; } } ret[i][j] = sum / cnt; } } return ret;}