解題區/解題區 - Zerojudge

b423. 魔術橡皮擦

contents

  1. 1. Problem
  2. 2. Sample Input
  3. 3. Sample Output
  4. 4. Solution

Problem

提供影像去背、相鄰去色兩種方案。

  • 去背對整張影像找像素差小於某一個範圍內，就將其 alpha 值設成 0。
  • 相鄰去色對鄰近四個方向上下左右進行搜索，將像素差低於某個閥值的都加入到集合中進行 alpha 值設成 0。

Sample Input

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0 0 0 0
3 2
1 2 3 255 4 5 6 255 7 8 9 255
10 11 12 255 13 14 15 255 16 17 18 255

Sample Output

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3
3 2
1 2 3 0 4 5 6 255 7 8 9 255
10 11 12 255 13 14 15 255 16 17 18 255

Solution

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#include <bits/stdc++.h>
using namespace std;
int X, Y, TYPE, DIFF;
namespace Image {
    const int MAXN = 256;
    int n, m, rgba[MAXN][MAXN][4], used[MAXN][MAXN] = {};
    int RGB_diff(int x, int y, int a, int b) {
        return (rgba[x][y][0]-rgba[a][b][0])*(rgba[x][y][0]-rgba[a][b][0])+
                (rgba[x][y][1]-rgba[a][b][1])*(rgba[x][y][1]-rgba[a][b][1])+
                (rgba[x][y][2]-rgba[a][b][2])*(rgba[x][y][2]-rgba[a][b][2]);
    }
    void gTransparent(int x, int y, long long diff) {
        if (x < 0 || y < 0 || x >= m || y >= n || diff < 0)
            return ;
        diff = diff * diff;
        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (RGB_diff(x, y, i, j) <= diff)
                    rgba[i][j][3] = 0;
    }
    void lTransparent(int x, int y, int ox, int oy, long long diff) {
        if (ox < 0 || oy < 0 || ox >= m || oy >= n || diff < 0)
            return ;
        static const int dx[] = {0, 0, 1, -1};
        static const int dy[] = {1, -1, 0, 0};
        if (x < 0 || y < 0 || x >= m || y >= n)
            return ;
        if (RGB_diff(x, y, ox, oy) > diff * diff || used[x][y])
            return ;
        rgba[x][y][3] = 0, used[x][y] = 1;
        for (int i = 0; i < 4; i++)
            lTransparent(x+dx[i], y+dy[i], ox, oy, diff);
    }
    void print() {
        printf("%d %d\n", n, m);
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++)
                printf("%d %d %d %d%c", rgba[i][j][0], rgba[i][j][1], rgba[i][j][2], rgba[i][j][3], j == n-1 ? '\n' : ' ');
        }
    }
}
int main() {
    scanf("%d %d %d %d", &X, &Y, &TYPE, &DIFF);
    scanf("%d %d", &Image::n, &Image::m);
    for (int i = 0; i < Image::m; i++)
        for (int j = 0; j < Image::n; j++)
            for (int k = 0; k < 4; k++)
                scanf("%d", &Image::rgba[i][j][k]);
    swap(X, Y);
    if (TYPE == 0)
        Image::gTransparent(X, Y, DIFF);
    if (TYPE == 1)
        Image::lTransparent(X, Y, X, Y, DIFF);
    Image::print();
    return 0;
}