C# - Emgu CV - FindContours层次结构数据始终为null

时间:2017-01-10 02:08:36

标签: c# opencv emgucv contour

我正在C#EmguCV项目中进行轮廓查找。对于这个项目,我必须获得轮廓层次数据。我以前在C ++ OpenCV项目中使用过这个方法,所以我理解FindContours方法和Hierarchy信息的工作原理。请在下面找到相关代码:

Mat grayImage = new Mat(originalImage.Size, originalImage.Depth, 1);
Mat edges = new Mat(originalImage.Size, originalImage.Depth, 1);

CvInvoke.CvtColor(originalImage, grayImage, ColorConversion.Bgr2Gray);            
CvInvoke.Canny(grayImage, edges, 100, 200, 3);

var contours = new VectorOfVectorOfPoint();

Mat hierarchy = new Mat();
CvInvoke.FindContours(edges, contours, hierarchy, RetrType.Tree, ChainApproxMethod.ChainApproxSimple);

当我运行此代码时,可以按预期找到轮廓。此外,Hierarchy Mat对象似乎按预期填充,即1 x size of outputResult x 4(参见下图),但此对象中的数据仍为null

Screenshot of hierarchy mat object

我无法找到有关如何从此对象中提取层次结构轮廓(树)数据的答案。我在other StackOverflow posts (see also the comments)看到其他人一直在努力和/或EmguCV 3.x库中可能存在错误,但我找不到答案。

我的问题是:Hierarchy Mat对象中的数据字段是null是否正常?

  • 如果是这样:如何从此Mat对象中提取相关的分层数据?
  • 如果没有:有没有办法规避分层数据为null的错误?例如是否可以降级到EmguCV 2.x?

2 个答案:

答案 0 :(得分:1)

也许已经晚了,但是......

你可以试试这个:

using (VectorOfVectorOfPoint vecVecPts2 = new VectorOfVectorOfPoint())
{

    int[,] hierarchy = CvInvoke.FindContourTree(img3, vecVecPts2, 
    ChainApproxMethod.ChainApproxNone);
}

或: more info

        /// >>>>Based on [joshuanapoli] answer<<<
        /// <summary>
        /// Get a neighbor index in the heirarchy tree.
        /// </summary>
        /// <returns>
        /// A neighbor index or -1 if the given neighbor does not exist.
        /// </returns>
        //public int Get(HierarchyIndex component, int index)
        //public int GetHierarchy(Mat Hierarchy, int contourIdx, int component)
        public int[] GetHierarchy(Mat Hierarchy, int contourIdx)
        {
            int[] ret = new int[] { };

            if (Hierarchy.Depth != Emgu.CV.CvEnum.DepthType.Cv32S)
            {
                throw new ArgumentOutOfRangeException("ContourData must have Cv32S hierarchy element type.");
            }
            if (Hierarchy.Rows != 1)
            {
                throw new ArgumentOutOfRangeException("ContourData must have one hierarchy hierarchy row.");
            }
            if (Hierarchy.NumberOfChannels != 4)
            {
                throw new ArgumentOutOfRangeException("ContourData must have four hierarchy channels.");
            }
            if (Hierarchy.Dims != 2)
            {
                throw new ArgumentOutOfRangeException("ContourData must have two dimensional hierarchy.");
            }
            long elementStride = Hierarchy.ElementSize / sizeof(Int32);
            var offset0 = (long)0 + contourIdx * elementStride;
            if (0 <= offset0 && offset0 < Hierarchy.Total.ToInt64() * elementStride)
            {


                var offset1 = (long)1 + contourIdx * elementStride;
                var offset2 = (long)2 + contourIdx * elementStride;
                var offset3 = (long)3 + contourIdx * elementStride;

                ret = new int[4];

                unsafe
                {
                    //return *((Int32*)Hierarchy.DataPointer.ToPointer() + offset);

                    ret[0] = *((Int32*)Hierarchy.DataPointer.ToPointer() + offset0);
                    ret[1] = *((Int32*)Hierarchy.DataPointer.ToPointer() + offset1);
                    ret[2] = *((Int32*)Hierarchy.DataPointer.ToPointer() + offset2);
                    ret[3] = *((Int32*)Hierarchy.DataPointer.ToPointer() + offset3);
                }


            }
            //else
            //{
            //    return new int[] { };
            //}

            return ret;
        }

答案 1 :(得分:0)

这对我有用:

Mat hierarchy = new Mat();

CvInvoke.FindContours(edges, contours, hierarchy, RetrType.Tree, ChainApproxMethod.ChainApproxSimple);

Array arr = hierarchy.GetData(true);

我将层次数据提取到dataGridView

        dataGridView1.Columns.Add("n-cont", "n-cont");
        dataGridView1.Columns.Add("next", "next");
        dataGridView1.Columns.Add("prev", "prev");

        dataGridView1.Columns.Add("f-child", "f-child");
        dataGridView1.Columns.Add("parent", "parent");


        for (int y = 0; y < hier.Cols; y++)
        {

            dataGridView1.Rows.Add(y.ToString(), arr.GetValue(0, y, 0).ToString(), arr.GetValue(0, y, 1).ToString()
                , arr.GetValue(0, y, 2).ToString(), arr.GetValue(0, y, 3).ToString());

        }

层次结构Mat中的数据被放入(1行,用于cols的n个(轮廓数),4个通道 (下一个,previos,第一个孩子,父母)