dng_to_png.py

# Copyright 2019-2020 by Andrey Ignatov. All Rights Reserved.

# python dng_to_png.py path_to_my_dng_file.dng

import numpy as np
import imageio
import rawpy
import sys
import os


def extract_bayer_channels(raw):

    ch_B  = raw[1::2, 1::2]
    ch_Gb = raw[0::2, 1::2]
    ch_R  = raw[0::2, 0::2]
    ch_Gr = raw[1::2, 0::2]

    return ch_R, ch_Gr, ch_B, ch_Gb


if __name__ == "__main__":

    raw_file = sys.argv[1]
    print("Converting file " + raw_file)

    if not os.path.isfile(raw_file):
        print("The file doesn't exist!")
        sys.exit()

    raw = rawpy.imread(raw_file)
    raw_image = raw.raw_image
    del raw

    # Use the following code to rotate the image (if needed)
    # raw_image = np.rot90(raw_image, k=2)

    raw_image = raw_image.astype(np.float32)
    ch_R, ch_Gr, ch_B, ch_Gb = extract_bayer_channels(raw_image)

    png_image = raw_image.astype(np.uint16)
    new_name = raw_file.replace(".dng", ".png")
    imageio.imwrite(new_name, png_image)