C++代码实现：

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//泛洪法，消耗大量空间，利用堆栈，容易造成堆栈溢出，在vs2019运行情况下需要调整安全堆栈内存大小才能正常运行
void seed_filling(HDC hdc, int x, int y, COLORREF fill_color, COLORREF boundary_color) {
    COLORREF c;
    c = GetPixel(hdc,x, y);
    if ((c != boundary_color) && (c != fill_color)) {
        SetPixel(hdc, x, y, fill_color);
        seed_filling(hdc, x + 1, y, fill_color, boundary_color);
        seed_filling(hdc, x - 1, y, fill_color, boundary_color);
        seed_filling(hdc, x, y + 1, fill_color, boundary_color);
        seed_filling(hdc, x, y - 1, fill_color, boundary_color);
        /*seed_filling(hdc, x + 1, y + 1, fill_color, boundary_color);
        seed_filling(hdc, x + 1, y - 1, fill_color, boundary_color);
        seed_filling(hdc, x - 1, y + 1, fill_color, boundary_color);
        seed_filling(hdc, x - 1, y - 1, fill_color, boundary_color);*/
    }
}

//扫描线种子填色算法，节约空间
void ScanFill4(HDC hdc, int x, int y, COLORREF fill_color, COLORREF boundary_color) {
    int xl, xr;
    bool spanNeedFill;
    POINT pt;
    POINT fillPoint;
    fillPoint.x = x;
    fillPoint.y = y;
    COLORREF c;
    c = GetPixel(hdc, x, y);
    stack<POINT> Stack;
    
    pt.x = fillPoint.x;
    pt.y = fillPoint.y;
    Stack.push(pt);
    while (!Stack.empty()) {
        pt = Stack.top();
        Stack.pop();
        fillPoint.y = pt.y;
        fillPoint.x = pt.x;
        while (GetPixel(hdc, fillPoint.x, fillPoint.y) == c) {
            SetPixel(hdc, fillPoint.x, fillPoint.y, fill_color);
            fillPoint.x++;
        }
        xr = fillPoint.x - 1;
        fillPoint.x = pt.x - 1;

        while (GetPixel(hdc, fillPoint.x, fillPoint.y) == c) {
            SetPixel(hdc, fillPoint.x, fillPoint.y, fill_color);
            fillPoint.x--;
        }
        xl = fillPoint.x + 1;

        for (int i = 0; i < 2; i++) {
            fillPoint.x = xl;
            if (i == 0) fillPoint.y = fillPoint.y + 1;
            else fillPoint.y = fillPoint.y - 2;
            while (fillPoint.x < xr) {
                spanNeedFill = FALSE;
                while (GetPixel(hdc, fillPoint.x, fillPoint.y) == c) {
                    spanNeedFill = TRUE;
                    fillPoint.x++;
                }
                if (spanNeedFill) {
                    pt.x = fillPoint.x - 1;
                    pt.y = fillPoint.y;
                    Stack.push(pt);
                    spanNeedFill = FALSE;
                }
                while (GetPixel(hdc, fillPoint.x, fillPoint.y) != c && fillPoint.x < xr) {
                    fillPoint.x++;
                }
            }
        }
    }
}