找到给定一组点的区域

Question

给定x,y坐标和已知宽度和高度的列表,如何确定封闭区域的NUMBER(在C#中)？

例如:

在此图像中,定义了5个附加区域:

1. 面子(1)
2. 眼睛(2)
3. 鼻子(1)
4. 面对面(1)

x,y点的列表将是黑色的任何像素,包括嘴.

Answer 1

您可以使用这个简单的算法，基于使用辅助位图进行洪水填充的思想：

// backColor is an INT representation of color at fillPoint in the beginning.
// result in pixels of enclosed shape.
private int GetFillSize(Bitmap b, Point fillPoint)
{
   int count = 0;
   Point p;
   Stack pixels = new Stack();
   var backColor = b.GetPixel(fillPoint.X, fillPoint.Y);
   pixels.Push(fillPoint);
   while (pixels.Count != 0)
   {
       count++;

       p = (Point)pixels.Pop();
       b.SetPixel(p.X, p.Y, backColor);

       if (b.GetPixel(p.X - 1, p.Y).ToArgb() == backColor)
           pixels.Push(new Point(p.X - 1, p.Y));

       if (b.GetPixel(p.X, p.Y - 1).ToArgb() == backColor)
           pixels.Push(new Point(p.X, p.Y - 1));

       if (b.GetPixel(p.X + 1, p.Y).ToArgb() == backColor)
           pixels.Push(new Point(p.X + 1, p.Y));

       if (b.GetPixel(p.X, p.Y + 1).ToArgb() == backColor)
           pixels.Push(new Point(p.X, p.Y + 1));
   }

   return count;
}

更新

上面的代码仅适用于这个四重链接的封闭区域。以下代码适用于八联封闭区域。

// offset points initialization.
Point[] Offsets = new Point[]
{
    new Point(-1, -1),
    new Point(-0, -1),
    new Point(+1, -1),
    new Point(+1, -0),
    new Point(+1, +1),
    new Point(+0, +1),
    new Point(-1, +1),
    new Point(-1, +0),
};

...

private int Fill(Bitmap b, Point fillPoint)
{
    int count = 0;
    Point p;
    Stack<Point> pixels = new Stack<Point>();
    var backColor = b.GetPixel(fillPoint.X, fillPoint.Y).ToArgb();
    pixels.Push(fillPoint);
    while (pixels.Count != 0)
    {
        count++;

        p = (Point)pixels.Pop();
        b.SetPixel(p.X, p.Y, Color.FromArgb(backColor));

        foreach (var offset in Offsets)
            if (b.GetPixel(p.X + offset.X, p.Y + offset.Y).ToArgb() == backColor)
                pixels.Push(new Point(p.X + offset.X, p.Y + offset.Y));
    }

    return count;
}

下面的图片清楚地表明了我的意思。此外，还可以向偏移数组添加更多远点，以便能够填充有间隙的区域。