OpenCVSharp 小练习最大内接矩形

最新推荐文章于 2025-11-30 02:02:14 发布

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本文介绍了一种基于OpenCV的内接矩形算法实现，该算法能够在二值化后的图像中找到最大内接矩形，并将其标记出来。通过遍历连通组件，算法以图像中心为起点，向外扩展寻找矩形边界。

参考：

https://blog.youkuaiyun.com/qq_35054151/article/details/88952728

注意：

这个可能不是最大内接矩形。

输入图像：

输出图像：

代码：

        public void Main()
        {
            Mat src = Cv2.ImRead(FilePath.Image.Shapes, ImreadModes.AnyColor);
            Mat gray = new Mat();
            Mat binary = new Mat();
            Cv2.CvtColor(src, gray, ColorConversionCodes.RGB2GRAY);
            Cv2.Threshold(gray, binary, 10, 255, ThresholdTypes.Binary);
            ConnectedComponents cc = Cv2.ConnectedComponentsEx(binary);
            foreach (var maxBlob in cc.Blobs.Skip(1))
            {
                Mat m = new Mat(binary, maxBlob.Rect);
                Rect rr = InSquare(m, new Point(m.Width / 2, m.Height / 2));
                Cv2.Rectangle(src, new Rect(maxBlob.Left + rr.Left, maxBlob.Top + rr.Top, rr.Width, rr.Height), Scalar.Red);
            }
            
        }

        /// <summary>
        /// 内接矩形
        /// </summary>
        /// <param name="img"></param>
        /// <param name="center"></param>
        /// <returns></returns>
        Rect InSquare(Mat img, Point center)
        {

            int[] edge = new int[4];
            edge[0] = center.Y - 1;//top
            edge[1] = center.X + 1;//right
            edge[2] = center.Y + 1;//bottom
            edge[3] = center.X - 1;//left
 
            bool[] EXPAND = { true, true, true, true };
            int n = 0;
            while (EXPAND[0] || EXPAND[1] || EXPAND[2] || EXPAND[3])
            {
                int edgeID = n % 4;
                EXPAND[edgeID] = ExpandEdge(img, edge, edgeID, EXPAND);
                n++;

            }


            Point tl = new Point(edge[3], edge[0]);
            Point br = new Point(edge[1], edge[2]);
            return new Rect(tl, new Size(br.X - tl.X, br.Y - tl.Y));
        }

        /// <summary>
        /// 扩展边界函数
        /// </summary>
        /// <param name="img"></param>
        /// <param name="edge">边界数组，存放4条边界值</param>
        /// <param name="edgeID">当前边界号</param>
        /// <returns>确定当前边界是否可以扩展</returns>
        bool ExpandEdge(Mat img, int[] edge, int edgeID, bool[] EXPAND)
        {


            int width = img.Width;
            int height = img.Height;

            switch (edgeID)
            {

                //top
                case 0:
                    if (!EXPAND[0]) return false;
                    if (edge[0] <= 1)
                        return false;
                    for (int i = edge[3] + 1; i < edge[1]; ++i) // left - right
                    {
                        if (img.Get<byte>(edge[0], i) == 0)
                        {
                            Console.WriteLine("top");

                            return false;
                        }
                        else
                            img.Set<byte>(edge[0], i, 100);
                    }
                    edge[0]--;
                    return true;
                //right
                case 1:
                    if (!EXPAND[1]) return false;
                    if (edge[1] >= width)
                        return false;
                    for (int i = edge[0] + 1; i < edge[2]; ++i)   // top - bottom
                    {
                        if (img.Get<byte>(i, edge[1]) == 0)
                        {
                            Console.WriteLine("right");
                            return false;
                        }
                        else
                            img.Set<byte>(i, edge[1], 50);
                    }
                    edge[1]++;
                    return true;

                //botton
                case 2:
                    if (!EXPAND[2]) return false;
                    if (edge[2] >= height)
                        return false;
                    for (int i = edge[3] + 1; i < edge[1]; ++i)  // left - right
                    {
                        if (img.Get<byte>(edge[2], i) == 0)
                        {
                            Console.WriteLine("botton");
                            return false;
                        }
                        else
                            img.Set<byte>(edge[2], i, 100);
                    }
                    edge[2]++;
                    return true;

                //left
                case 3:
                    if (!EXPAND[3]) return false;
                    if (edge[3] < 1)
                        return false;
                    for (int i = edge[0] + 1; i < edge[2]; ++i) // top - bottom
                    {
                        if (img.Get<byte>(i, edge[3]) == 0)
                        {
                            Console.WriteLine("left");
                            return false;
                        }
                        else
                            img.Set<byte>(i, edge[3], 50);
                    }
                    edge[3]--;
                    return true;

                default:
                    return false;

            }

        }