This script converts from a simple binary elevation format to ArcASCII.

convert_grid.py

"""
This script converts from a simple binary elevation format to ArcASCII. The format of the binary file is:

Offset    Type    Description
-----------------------------
0         uint    Grid width
4         uint    Grid height
8         float*  Elevation values as floats in row-major order from lower-left to upper-right.
"""

import os
import struct
import sys


# input() in Py2 processes numbers only, so map to raw_input
if sys.version_info[0] < 3:
    input = raw_input


def main():
    if len(sys.argv) < 3:
        print('Usage: convert_grid.py <input grid> <output grid>')
        sys.exit(-1)

    input_path, output_path = sys.argv[1:3]

    if os.path.exists(output_path):
        overwrite_message = '{0} already exists. Overwrite? [y/n] '.format(output_path)
        if not input(overwrite_message).lower().startswith('y'):
            sys.exit(-1)

    with open(output_path, 'w') as f_out:
        with open(input_path, 'rb') as f_in:
            width, height = struct.unpack('II', f_in.read(8))

            f_in.seek(0, os.SEEK_END)
            assert f_in.tell() == width * height * 4 + 8

            header = [
                'ncols {0}'.format(width),
                'nrows {0}'.format(height),
                'xllcorner 0.0',
                'yllcorner 0.0',
                'cellsize 1.0',
                'NODATA_value -9999',
                ''
            ]
            f_out.write('\n'.join(header))

            # The binary format orders rows from bottom to top, while the ArcASCII format orders top to bottom.
            # So we'll read from the end of the binary file backwards
            for i in range(1, height + 1):
                f_in.seek(-i * width * 4, os.SEEK_END)
                row = struct.unpack('f' * width, f_in.read(width * 4))
                line = (str(x) for x in row)
                f_out.write(' '.join(line) + '\n')


if __name__ == '__main__':
    main()