from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import numpy as np
import sys

def write_pfm(file, image, scale=1):
    file = open(file, 'wb')

    color = None

    if image.dtype.name != 'float32':
        raise Exception('Image dtype must be float32.')

    image = np.flipud(image)

    if len(image.shape) == 3 and image.shape[2] == 3:  # color image
        color = True
    elif len(image.shape) == 2 or len(
            image.shape) == 3 and image.shape[2] == 1:  # greyscale
        color = False
    else:
        raise Exception(
            'Image must have H x W x 3, H x W x 1 or H x W dimensions.')

    file.write(b'PF\n' if color else b'Pf\n')
    file.write(b'%d %d\n' % (image.shape[1], image.shape[0]))

    endian = image.dtype.byteorder

    if endian == '<' or endian == '=' and sys.byteorder == 'little':
        scale = -scale

    file.write(b'%f\n' % scale)

    image.tofile(file)