Li Kou daily question - day 42 -661. Picture smoother

2022.7.25 Did you brush the questions today ？

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subject ：

Image smoother It's the size of  3 x 3 Filter , Used to smooth each cell of the image , The value of the cell after smoothing is the average gray level of the cell .

Of each cell    Average grayscale Defined as ： The cell itself and its surroundings 8 Average of cells , The result needs to be rounded down .（ namely , You need to calculate... In the blue smoother 9 Average of cells ）.

If there is a missing cell around a cell , The missing cells are not considered when calculating the average gray level （ namely , You need to calculate... In the red smoother 4 Average of cells ）.

analysis ：

A two-dimensional array , Find the effective lattice around each lattice （ Valuable ） Average value , Then the average value of each two-dimensional array element is calculated to construct a new two-dimensional array .

Ideas ： First, make it convenient for two-dimensional arrays , For the first 【0】【0】 Subscript element , We look around it 8 Lattice , And find 【0】【1】 The surrounding 8 Lattice , For this 8 Judge whether it is effective by a grid, and then calculate the average value .

analysis ：

1. Violence law

class Solution {
public:
    vector<vector<int>> imageSmoother(vector<vector<int>>& img) {
        int m = img.size(), n = img[0].size();
        vector<vector<int>> ret(m, vector<int>(n));
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int num = 0, sum = 0;
                for (int x = i - 1; x <= i + 1; x++) {
                    for (int y = j - 1; y <= j + 1; y++) {
                        if (x >= 0 && x < m && y >= 0 && y < n) {
                            num++;
                            sum += img[x][y];
                        }
                    }
                }
                ret[i][j] = sum / num;
            }
        }
        return ret;
    }
};