point_cloud2.py

#!/usr/bin/env python

"""
Serialization of sensor_msgs.PointCloud2 messages.

Author: Tim Field
"""

import roslib; roslib.load_manifest('sensor_msgs')
import roslib.message
import ctypes
import math
import struct

from sensor_msgs.msg import PointCloud2, PointField

_DATATYPES = {}
_DATATYPES[PointField.INT8]    = ('b', 1)
_DATATYPES[PointField.UINT8]   = ('B', 1)
_DATATYPES[PointField.INT16]   = ('h', 2)
_DATATYPES[PointField.UINT16]  = ('H', 2)
_DATATYPES[PointField.INT32]   = ('i', 4)
_DATATYPES[PointField.UINT32]  = ('I', 4)
_DATATYPES[PointField.FLOAT32] = ('f', 4)
_DATATYPES[PointField.FLOAT64] = ('d', 8)

def read_points(cloud, field_names=None, skip_nans=False, uvs=[]):
    """
    Read points from a L{sensor_msgs.PointCloud2} message.

    @param cloud: The point cloud to read from.
    @type  cloud: L{sensor_msgs.PointCloud2}
    @param field_names: The names of fields to read. If None, read all fields. [default: None]
    @type  field_names: iterable
    @param skip_nans: If True, then don't return any point with a NaN value.
    @type  skip_nans: bool [default: False]
    @param uvs: If specified, then only return the points at the given coordinates. [default: empty list]
    @type  uvs: iterable
    @return: Generator which yields a list of values for each point.
    @rtype:  generator
    """
    assert isinstance(cloud, roslib.message.Message) and cloud._type == 'sensor_msgs/PointCloud2', 'cloud is not a sensor_msgs.msg.PointCloud2'
    fmt = _get_struct_fmt(cloud.is_bigendian, cloud.fields, field_names)
    width, height, point_step, row_step, data, isnan = cloud.width, cloud.height, cloud.point_step, cloud.height*cloud.point_step, cloud.data, math.isnan
    unpack_from = struct.Struct(fmt).unpack_from

    if skip_nans:
        if uvs:
            for u, v in uvs:
                p = unpack_from(data, (row_step * v) + (point_step * u))
                has_nan = False
                for pv in p:
                    if isnan(pv):
                        has_nan = True
                        break
                if not has_nan:
                    yield p
        else:
            for v in xrange(height):
                offset = row_step * v
                for u in xrange(width):
                    p = unpack_from(data, offset)
                    has_nan = False
                    for pv in p:
                        if isnan(pv):
                            has_nan = True
                            break
                    if not has_nan:
                        yield p
                    offset += point_step
    else:
        if uvs:
            for u, v in uvs:
                yield unpack_from(data, (row_step * v) + (point_step * u))
        else:
            for v in xrange(height):
                offset = row_step * v
                for u in xrange(width):
                    yield unpack_from(data, offset)
                    offset += point_step

def create_cloud(header, fields, points):
    """
    Create a L{sensor_msgs.msg.PointCloud2} message.

    @param header: The point cloud header.
    @type  header: L{std_msgs.msg.Header}
    @param fields: The point cloud fields.
    @type  fields: iterable of L{sensor_msgs.msg.PointField}
    @param points: The point cloud points.
    @type  points: list of iterables, i.e. one iterable for each point, with the
                   elements of each iterable being the values of the fields for 
                   that point (in the same order as the fields parameter)
    @return: The point cloud.
    @rtype:  L{sensor_msgs.msg.PointCloud2}
    """

    cloud_struct = struct.Struct(_get_struct_fmt(False, fields))

    buff = ctypes.create_string_buffer(cloud_struct.size * len(points))

    point_step, pack_into = cloud_struct.size, cloud_struct.pack_into
    offset = 0
    for p in points:
        pack_into(buff, offset, *p)
        offset += point_step

    return PointCloud2(header=header,
                       height=1,
                       width=len(points),
                       is_dense=False,
                       is_bigendian=False,
                       fields=fields,
                       point_step=cloud_struct.size,
                       row_step=cloud_struct.size * len(points),
                       data=buff.raw)

def create_cloud_xyz32(header, points):
    """
    Create a L{sensor_msgs.msg.PointCloud2} message with 3 float32 fields (x, y, z).

    @param header: The point cloud header.
    @type  header: L{std_msgs.msg.Header}
    @param points: The point cloud points.
    @type  points: iterable
    @return: The point cloud.
    @rtype:  L{sensor_msgs.msg.PointCloud2}
    """
    fields = [PointField('x', 0, PointField.FLOAT32, 1),
              PointField('y', 4, PointField.FLOAT32, 1),
              PointField('z', 8, PointField.FLOAT32, 1)]
    return create_cloud(header, fields, points)

def _get_struct_fmt(is_bigendian, fields, field_names=None):
    fmt = '>' if is_bigendian else '<'

    offset = 0
    for field in (f for f in sorted(fields, key=lambda f: f.offset) if field_names is None or f.name in field_names):
        if offset < field.offset:
            fmt += 'x' * (field.offset - offset)
            offset = field.offset
        if field.datatype not in _DATATYPES:
            print >> sys.stderr, 'Skipping unknown PointField datatype [%d]' % field.datatype
        else:
            datatype_fmt, datatype_length = _DATATYPES[field.datatype]
            fmt    += field.count * datatype_fmt
            offset += field.count * datatype_length

    return fmt