How to fill enclosed area in the Bitmap object wit

Question

Give point within the region with a color to fill the region, similar to the "drawing" in the paint bucket function.
The. NET Framework, there is no direct equivalent.
but i hope use C# to do it.
is it possible?

Answer 1

Here's a very naive flood fill algorithm that should get you started

void Form1_Paint(object sender, PaintEventArgs e)
{
    using (Bitmap bitmap = new Bitmap(500, 500))
    {
        using (Graphics g = Graphics.FromImage(bitmap))
        {
            g.Clear(Color.White);
            List<Point> points = new List<Point>();
            for (double i = 0; i < 10; i++)
            {
                double dist = (i % 2 == 0) ? 100 : 50;
                double x = 200 + Math.Cos(i / 10d * Math.PI * 2d) * dist;
                double y = 200 + Math.Sin(i / 10d * Math.PI * 2d) * dist;
                points.Add(new Point((int)x, (int)y));
            }
            g.DrawPolygon(Pens.Black, points.ToArray());
        }

        FloodFill(bitmap, 200, 200, Color.Red);

        e.Graphics.DrawImage(bitmap, 0, 0);
    }
}

void FloodFill(Bitmap bitmap, int x, int y, Color color)
{
    BitmapData data = bitmap.LockBits(
        new Rectangle(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
    int[] bits = new int[data.Stride / 4 * data.Height];
    Marshal.Copy(data.Scan0, bits, 0, bits.Length);

    LinkedList<Point> check = new LinkedList<Point>();
    int floodTo = color.ToArgb();
    int floodFrom = bits[x + y * data.Stride / 4];
    bits[x + y * data.Stride / 4] = floodTo;

    if (floodFrom != floodTo)
    {
        check.AddLast(new Point(x, y));
        while (check.Count > 0)
        {
            Point cur = check.First.Value;
            check.RemoveFirst();

            foreach (Point off in new Point[] {
                new Point(0, -1), new Point(0, 1), 
                new Point(-1, 0), new Point(1, 0)})
            {
                Point next = new Point(cur.X + off.X, cur.Y + off.Y);
                if (next.X >= 0 && next.Y >= 0 &&
                    next.X < data.Width &&
                    next.Y < data.Height)
                {
                    if (bits[next.X + next.Y * data.Stride / 4] == floodFrom)
                    {
                        check.AddLast(next);
                        bits[next.X + next.Y * data.Stride / 4] = floodTo;
                    }
                }
            }
        }
    }

    Marshal.Copy(bits, 0, data.Scan0, bits.Length);
    bitmap.UnlockBits(data);
}