Add clouds/meshes file format converter

[VictorLamoine]

Aims to replace:

convert_pcd_ascii_binary.cpp
pcd2ply.cpp
obj2pcd.cpp
obj2ply.cpp
obj2vtk.cpp
pcd2ply.cpp
pcd2vtk.cpp
ply2pcd.cpp
ply2vtk.cpp
vtk2obj.cpp
vtk2pcd.cpp
vtk2ply.cpp

This will also add STL format converter.

[VictorLamoine]

A first review would be appreciated, the program is working fine though I have not extensively tested it.

[SergioRAgostinho]

I would return 0 here.

[VictorLamoine]

Agreed

[SergioRAgostinho]

Looking forward to see this merged :)

[VictorLamoine]

I think I fixed everything above, the program is now "finished".
Color is lost during conversion into an OBJ file, thats the only issue I have identified right now.

Give it a test and tell me if something is wrong!

[SergioRAgostinho]

This warning will also be printed in saveMesh() better to just remove it. This branch of your if statement can pretty much disappear and be moved to the else branch with ply and vtk.

[VictorLamoine]

True, I fixed that. Interestingly savePolygonFile does not allow to save OBJ files.

[SergioRAgostinho]

Looked at the source and it definitely looks like bug, especially given the fact that you can load OBJ files in the function above :D

If you patched it you could even move L155-165 into L174-188 adding the additional check for the output_type.

[SergioRAgostinho]

Forget about my last suggestion. I just noticed that there are seemingly close functionalities implemented in pcl::io::save and pcl::io::savePolygonFile. This should probably be addressed in another pull request. Thanks for you effort!

[VictorLamoine]

I've just added an option to transform a mesh into a point cloud using the -c or --cloud switches. It just discards all faces in the file.

[SergioRAgostinho]

Sorry, I wasn't clear enough on my last comment about the warning. Note that L102-110 are similar to L139-144, which basically means you can delete L102-110.

[VictorLamoine]

Oh that's right I must have not read the right lines when reading your comment 😄
All of these remarks makes the code much cleaner!

[VictorLamoine]

@jspricke Friendly pi(n)g 🐷

[jspricke]

Can you update the copyright?

[taketwo]

Victor, great work!

I find the filename argument handling to be unnecessary verbose though. Instead of lines 213-217, 223-228, 247-265 we can write something like (untested):

const std::vector<std::string> supported_extensions = {".obj", ".pcd", ".ply", ".stl", ".vtk"};
std::vector<int> file_args;
for (int i = 1; i < argc; ++i)
  for (size_t j = 0; j < supported_extensions.size (); ++j)
    if (boost::algorithm::ends_with (argv[i], supported_extensions[j])
    {
      file_args.push_back (i);
      break;
    }

if (file_args.size () != 2)
  // error message, return

std::string input = argv[file_args[0]];
std::string output = argv[file_args[1]];

[VictorLamoine]

I've done it your way Sergey, it's shorter and still very readable. I did not use the C++11 vector initializer because C++11 is not enabled in PCL.

[taketwo]

I did not use the C++11 vector initializer because C++11 is not enabled in PCL.

Yeah, right, I suspected that line would not compile with the old standard :)

What about the name of the tool, maybe just pcl_converter or pcl_convert?

[VictorLamoine]

Now it's named pcl_converter

[taketwo]

Thanks! I haven't tried it, but the code looks good for me.

Do we want to merge this before the release or immediately after?

[VictorLamoine]

I don't mind; I think it's a useful tool so I would merge before.
One more thing to add to your giant changelog :)

[SergioRAgostinho]

Agree with Victor on both statements. Kudos for your massive changelog Sergey ;)

[taketwo]

Thanks guys.
@jspricke please merge if you think it's ready.