PCL Save VTK File With Texture Coordinates 使用PCL库来保存带纹理坐标的VTK文件

我之前有一篇博客Convert PLY to VTK Using PCL 1.6.0 or PCL 1.8.0 使用PCL库将PLY格式转为VTK格式展示了如何将PLY格式文件转化为VTK格式的文件，在文章的最后提到了VTK文件保存纹理的两种方式，第一种是需要有texture的图片，然后每个点存储上该点在图片中的x，y坐标，一般会normalize到[0,1]之间。第二种方法是直接存每个点的rgb值，上面的方法用的是第二种，因为导入的PLY格式就直接存储的texture的rgb值，并没有额外提供texture图片。

对于一般的PLY或者PCD格式的点云，一般都是用第二种方式来保存纹理的，即直接存储rgb值，这样转换成的vtk文件自然也是第二种情况，而对于大多数的可视化软件，比如ParaView或者3D Slicer，貌似只支持第一种方式，即需要导入texture图片(如果大家知道直接显示rgb值的方法，请在下方留言告知博主)。这样就极大的不方便了，而且PCL库中的点云格式一般也是XYZRGBA，并没有带UV，纹理有专门的数据结构。我们的目标是生成带texture coordinates的VTK文件，那么可以通过修改pcl自带的saveVTKFile函数来实现目标。

 

这里我们把纹理坐标单独抽出来，用下面的数据结构来表示：

std::vector<Eigen::Vector2f> texcoord;

 

pcl自带的pcl::io::saveVTKFile函数所在的文件的地址是.../io/src/vtk_io.cpp。默认的是写入RGB的值，我们只需要注释掉写入RGB的部分，添加上写入纹理坐标的部分:

 

Using PCL 1.6.0

// PCL 1.6.0
int save_vtk_file(const std::string &file_name,                   const sensor_msgs::PointCloud2 &cloud,                   const std::vector<Eigen::Vector2f>& texcoord,                  unsigned precision) {    if (cloud.data.empty ())    {        PCL_ERROR ("[pcl::io::saveVTKFile] Input point cloud has no data!\n");        return (-1);    }    // Open file    std::ofstream fs;    fs.precision (precision);    fs.open (file_name.c_str ());    unsigned int nr_points  = cloud.width * cloud.height;    unsigned int point_size = static_cast<unsigned int> (cloud.data.size () / nr_points);    // Write the header information    fs << "# vtk DataFile Version 3.0\nvtk output\nASCII\nDATASET POLYDATA\nPOINTS " << nr_points << " float" << std::endl;    // Iterate through the points    for (unsigned int i = 0; i < nr_points; ++i)    {        int xyz = 0;        for (size_t d = 0; d < cloud.fields.size (); ++d)        {            int count = cloud.fields[d].count;            if (count == 0)                count = 1;          // we simply cannot tolerate 0 counts (coming from older converter code)            int c = 0;            if ((cloud.fields[d].datatype == sensor_msgs::PointField::FLOAT32) && (                cloud.fields[d].name == "x" ||                 cloud.fields[d].name == "y" ||                 cloud.fields[d].name == "z"))            {                float value;                memcpy (&value, &cloud.data[i * point_size + cloud.fields[d].offset + c * sizeof (float)], sizeof (float));                fs << value;                if (++xyz == 3)                    break;            }            fs << " ";        }        if (xyz != 3)        {            PCL_ERROR ("[pcl::io::saveVTKFile] Input point cloud has no XYZ data!\n");            return (-2);        }        fs << std::endl;    }    // Write vertices    fs << "\nVERTICES " << nr_points << " " << 2*nr_points << std::endl;    for (unsigned int i = 0; i < nr_points; ++i)        fs << "1 " << i << std::endl;    // Write RGB values//     int field_index = pcl::getFieldIndex (cloud, "rgb");//     if (field_index != -1)//     {//         fs << "\nPOINT_DATA " << nr_points << "\nCOLOR_SCALARS scalars 3\n";//         for (unsigned int i = 0; i < nr_points; ++i)//         {//             int count = cloud.fields[field_index].count;//             if (count == 0)//                 count = 1;          // we simply cannot tolerate 0 counts (coming from older converter code)//             int c = 0;//             if (cloud.fields[field_index].datatype == sensor_msgs::PointField::FLOAT32)//             {//                 pcl::RGB color;//                 memcpy (&color, &cloud.data[i * point_size + cloud.fields[field_index].offset + c * sizeof (float)], sizeof (pcl::RGB));//                 int r = color.r;//                 int g = color.g;//                 int b = color.b;//                 fs << static_cast<float> (r) / 255.0f << " " << static_cast<float> (g) / 255.0f << " " << static_cast<float> (b) / 255.0f;//             }//             fs << std::endl;//         }//     }    // Write texture coordinates    fs << "\nPOINT_DATA " << nr_points << "\nTEXTURE_COORDINATES tcoords 2 float\n";    for (unsigned int i = 0; i < nr_points; ++i) {            //fs << texcoord[i][0] << " " << texcoord[i][1] << "\n";        fs << texcoord[i][1] << " " << texcoord[i][0] << "\n";    }    fs << std::endl;    // Close file    fs.close ();    return (0);}

 

Using PCL 1.8.0

// PCL 1.8.0int save_vtk_file (const std::string &file_name,     const pcl::PCLPointCloud2 &cloud,     const std::vector<Eigen::Vector2f>& texcoord,    unsigned precision){    if (cloud.data.empty ())    {        PCL_ERROR ("[pcl::io::saveVTKFile] Input point cloud has no data!\n");        return (-1);    }    // Open file    std::ofstream fs;    fs.precision (precision);    fs.open (file_name.c_str ());    unsigned int nr_points  = cloud.width * cloud.height;    unsigned int point_size = static_cast<unsigned int> (cloud.data.size () / nr_points);    // Write the header information    fs << "# vtk DataFile Version 3.0\nvtk output\nASCII\nDATASET POLYDATA\nPOINTS " << nr_points << " float" << '\n';    // Iterate through the points    for (unsigned int i = 0; i < nr_points; ++i)    {        int xyz = 0;        for (size_t d = 0; d < cloud.fields.size (); ++d)        {            int count = cloud.fields[d].count;            if (count == 0)                count = 1;          // we simply cannot tolerate 0 counts (coming from older converter code)            int c = 0;            if ((cloud.fields[d].datatype == pcl::PCLPointField::FLOAT32) && (                cloud.fields[d].name == "x" ||                 cloud.fields[d].name == "y" ||                 cloud.fields[d].name == "z"))            {                float value;                memcpy (&value, &cloud.data[i * point_size + cloud.fields[d].offset + c * sizeof (float)], sizeof (float));                fs << value;                if (++xyz == 3)                    break;            }            fs << " ";        }        if (xyz != 3)        {            PCL_ERROR ("[pcl::io::saveVTKFile] Input point cloud has no XYZ data!\n");            return (-2);        }        fs << '\n';    }    // Write vertices    fs << "\nVERTICES " << nr_points << " " << 2*nr_points << '\n';    for (unsigned int i = 0; i < nr_points; ++i)        fs << "1 " << i << '\n';//     // Write RGB values//     int field_index = getFieldIndex (cloud, "rgb");//     if (field_index != -1)//     {//         fs << "\nPOINT_DATA " << nr_points << "\nCOLOR_SCALARS scalars 3\n";//         for (unsigned int i = 0; i < nr_points; ++i)//         {//             int count = cloud.fields[field_index].count;//             if (count == 0)//                 count = 1;          // we simply cannot tolerate 0 counts (coming from older converter code)//             int c = 0;//             if (cloud.fields[field_index].datatype == pcl::PCLPointField::FLOAT32)//             {//                 pcl::RGB color;//                 memcpy (&color, &cloud.data[i * point_size + cloud.fields[field_index].offset + c * sizeof (float)], sizeof (RGB));//                 int r = color.r;//                 int g = color.g;//                 int b = color.b;//                 fs << static_cast<float> (r) / 255.0f << " " << static_cast<float> (g) / 255.0f << " " << static_cast<float> (b) / 255.0f;//             }//             fs << '\n';//         }//     }    // Write texture coordinates    fs << "\nPOINT_DATA " << nr_points << "\nTEXTURE_COORDINATES tcoords 2 float\n";    for (unsigned int i = 0; i < nr_points; ++i) {        //fs << texcoord[i][0] << " " << texcoord[i][1] << "\n";        fs << texcoord[i][1] << " " << texcoord[i][0] << "\n";    }    fs << '\n';    // Close file    fs.close ();    return (0);}