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https://github.com/dimatura/pypcd

PCL pcd fileformat i/o in Python
https://github.com/dimatura/pypcd

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PCL pcd fileformat i/o in Python

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README 

        
``pypcd``

=========



What?

-----



Pure Python module to read and write point clouds stored in the

`PCD file format `__,

used by the `Point Cloud Library `__.



Why?

----



You want to mess around with your point cloud data without writing C++

and waiting hours for the template-heavy PCL code to compile.



You tried to get some of the Python bindings for PCL to compile

and just gave up.



How does it work?

-----------------



It parses the PCD header and loads the data (whether in ``ascii``,

``binary`` or ``binary_compressed`` format) as a

`Numpy `__ structured array. It creates an

instance of the ``PointCloud``

class, containing the point cloud data as ``pc_data``, and

some convenience functions for I/O and metadata access.

See the comments in ``pypcd.py`` for some info on the point cloud

structure.



Example

-------



.. code:: python



    import pypcd

    # also can read from file handles.

    pc = pypcd.PointCloud.from_path('foo.pcd')

    # pc.pc_data has the data as a structured array

    # pc.fields, pc.count, etc have the metadata



    # center the x field

    pc.pc_data['x'] -= pc.pc_data['x'].mean()



    # save as binary compressed

    pc.save_pcd('bar.pcd', compression='binary_compressed')



How to install

--------------



.. code:: bash



    pip install pypcd



That's it! You may want to install optional dependencies such as `pandas

`__.



You can also clone this repo and use setup.py. 



.. code:: bash



    git clone https://github.com/dimatura/pypcd



Note that downloading data assets will

require `git-lfs `__.



Using with ROS

---------------



You can also use this library with ROS ``sensor_msgs``, but it is *not* a dependency.

You don't need to install this package with catkin -- using `pip` should be fine --

but if you want to it is possible:



Steps:



.. code:: bash



    # you need to do this manually in this case

    pip install python-lzf

    cd your_workspace/src

    git clone https://github.com/dimatura/pypcd

    mv setup_ros.py setup.py

    catkin build pypcd

    source ../devel/setup.bash



Then you can do something like this:



.. code:: python



    import pypcd

    import rospy

    from sensor_msgs.msg import PointCloud2



    def cb(msg):

        pc = PointCloud.from_msg(msg)

        pc.save('foo.pcd', compression='binary_compressed')

        # maybe manipulate your pointcloud

        pc.pc_data['x'] *= -1

        outmsg = pc.to_msg()

        # you'll probably need to set the header

        outmsg.header = msg.header

        pub.publish(outmsg)



    # ...

    sub = rospy.Subscriber('incloud', PointCloud2)

    pub = rospy.Publisher('outcloud', PointCloud2, cb)

    rospy.init('pypcd_node')

    rospy.spin()



Is it beautiful, production-ready code?

---------------------------------------



No.



What else can it do?

--------------------



There's a bunch of functionality accumulated

over time, much of it hackish and untested.

In no particular order,



-  Supports ``ascii``, ``binary`` and ``binary_compressed`` data.

   The latter requires the ``lzf`` module.

-  Decode and encode RGB into a single ``float32`` number. If

   you don't know what I'm talking about consider yourself lucky.

-  Point clouds to `pandas `__ dataframes. 

   This in particular is quite useful,

   since `pandas` is pretty powerful and makes various operations

   such as merging point clouds or manipulating values easy.

   Conceptually, data frames are a good match to the point cloud format, since

   many point clouds in reality have heterogeneous data types - e.g.

   `x`, `y` and `z` are float fields but `label` is an int.

-  Convert to and from `ROS `__ PointCloud2

   messages.

   Requires the ROS ``sensor_msgs`` package with Python bindings

   installed.

   This functionality uses code developed by Jon Binney under

   the BSD license, included as ``numpy_pc2.py``.



What can't it do?

-----------------



There's no synchronization between the metadata fields in

``PointCloud``

and the data in ``pc_data``. If you change the shape of ``pc_data``

without updating the metadata fields you'll run into trouble.



I've only used it for unorganized point cloud data

(in PCD conventions, ``height=1``), not organized

data like what you get from RGBD.

However, some things may still work.



While padding and fields with count larger

than 1 seem to work, this is a somewhat

ad-hoc aspect of the PCD format, so be careful.

If you want to be safe, you're probably better off

using neither -- just name each component

of your field something like ``FIELD_00``, ``FIELD_01``, etc.



It also can't run on Python 3, yet, but there's a PR to fix this

that might get pulled in the near future.



It's slow!

----------



Try using ``binary`` or ``binary_compressed``; using

ASCII is slow and takes up a lot of space, not to

mention possibly inaccurate if you're not careful

with how you format your floats.



I found a bug / I added a feature / I made your code cleaner

------------------------------------------------------------



Thanks! You can submit a pull request. But honestly, I'm not too good

at keeping up with my github :(



TODO

----



- Better API for various operations.

- Clean up, get rid of cruft.

- Add a cli for common use cases like file type conversion.

- Better support for structured point clouds, with tests.

- Better testing.

- Better docs. More examples.

- More testing of padding

- Improve handling of multicount fields

- Better support for rgb nonsense

- Export to ply?

- Figure out if it's acceptable to use "pointcloud" as a single word.

- Package data assets in pypi?



Credits

-------



The code for compressed point cloud data was informed by looking at

`Matlab

PCL `__.



@wkentaro for some minor changes.



I used `cookiecutter `__ to

help with the packaging.



The code in ``numpy_pc2.py`` was developed by Jon Binney under

the BSD license for `ROS `__.



I want to congratulate you / insult you

---------------------------------------



My email is ``[email protected]``.



Copyright (C) 2015-2017 Daniel Maturana