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
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
int 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); }
注意上面纹理的x和y的值，根据贴图的情况来看是否需要调换位置。
本文转自博客园Grandyang，原文链接：PCL Save VTK File With Texture Coordinates 使用PCL库来保存带纹理坐标的VTK文件
，如需转载请自行联系原博主。
