How do I save color to las file using laspy

Question

I have been trying to add color to my point cloud. I want to add red green and blue but for now, I am only adding red to simplify the problem. I want to be using chunks to read the file. Right now when I read the file back I get an array of zeros.

import numpy as np
import laspy

def calculate_normals(file: str, chunk_size: int):
    # read file point cloud file
    header = laspy.LasHeader(point_format=2, version="1.2")
    with laspy.open(file, mode='r') as read_f:

        n_points = int(read_f.header.point_count)
        n_chunks = int(n_points / chunk_size) + 1
        chunk_size = n_points // n_chunks + 1

        # Write to new file
        header.scales = read_f.header.scales
        out_file = file[:-4] + '_normals' + file[-4:]
        print('Opening', out_file)
        with laspy.open(out_file, mode='w', header=header) as write_f:
            for count, chunk in enumerate(read_f.chunk_iterator(chunk_size)):
                rec_s = len(chunk)
                header = laspy.LasHeader(point_format=2, version="1.2")
                point_record = laspy.ScaleAwarePointRecord.zeros(rec_s, header=header)
                points = np.array((chunk.x, chunk.y, chunk.z)).T
                point_record.x, point_record.y, point_record.z = points.T
                point_record.red = np.full(len(chunk), 155)

def read_test(file):
    with laspy.open(file, mode='r') as read_f:
        points = read_f.read_points(500)
        print(points.red)

Answer 1

You are modifying the point_record, but you don't seem to actually be writing it.

You have to use write_f.write_points