661. Image Smoother

Posted 2020-10-10 andywu

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].

题意：求矩阵每个位置的相邻8个位置加上本身的值的平均值。

 1     public int[][] imageSmoother(int[][] M) {
 2         if (M == null) {
 3             return null;
 4         }
 5         int rows = M.length;
 6         if (rows == 0) {
 7             return new int[0][];
 8         }
 9 
10         int cols = M[0].length;
11         int[][] rets = new int[rows][cols];
12         for (int row = 0; row < rows; row++) {
13             for (int col = 0; col < cols; col++) {
14                 int count = 0;
15                 int sum = 0;
16                 for (int incR : new int[]{-1, 0, 1}) {
17                     for (int incC : new int[]{-1, 0, 1}) {
18                         int r = row + incR;
19                         int c = col + incC;
20                         if (0 <= r && r < rows && 0 <= c && c < cols) {
21                             count++;
22                             sum += M[row + incR][col + incC];
23                         }
24                     }
25                 }
26                 rets[row][col] = sum / count;
27             }
28         }
29         return rets;
30     }