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The fix was actually to first remove the field_names from the read_points input parameters.

That way the function output 4 values per line instead of 3.

Taking the last value of that list and doing the required bitwise operations to retrieves the individual r,g,b values.

My code in case someone needs it in the future is the following:

import sensor_msgs.point_cloud2 as pc2
import ctypes
import struct
...............
# subscribe to pointcloud topic define the function that does the parsing
def PointCloud(self, PointCloud2):
    self.lock.acquire()
    gen = pc2.read_points(PointCloud2, skip_nans=True)
    int_data = list(gen)
    for x in int_data:
        test = x[3] 
        # cast float32 to int so that bitwise operations are possible
        s = struct.pack('>f' ,test)
        i = struct.unpack('>l',s)[0]
        # you can get back the float value by the inverse operations
        pack = ctypes.c_uint32(i).value
        r = (pack & 0x00FF0000)>> 16
        g = (pack & 0x0000FF00)>> 8
        b = (pack & 0x0000FF00)
        print r,g,b # prints r,g,b values in the 0-255 range
                    # x,y,z can be retrieved from the x[0],x[1],x[2]
    self.lock.release()