gltf_split_image.py

#!/usr/bin/env python3
# SPDX-License-Identifier: MIT

# Program to copy images referenced by glTF files.
# Run the program with --help argument for arguments.

import sys
import shutil
import os
import json

def gltf_copy_image(in_gltf_path, in_img_path, out_img_path):
	dic = None
	embedded_buffer = None
	with open(in_gltf_path, "rb") as f:
		h = f.read(12)
		if h[0:1] == b"\x7B":
			f.seek(0)
			dic = json.loads(f.read().decode("utf-8"))
		elif h[0:4] == b"glTF" and h[4:8] == b"\x02\x00\x00\x00":
			total_size = int.from_bytes(h[8:12], byteorder="little")
			while True:
				c = f.read(8)
				if len(c) != 8:
					break
				c_size = int.from_bytes(c[4:8], byteorder=little)
				if c == b"JSON":
					dic = json.loads(f.read(c_size).decode("utf-8"))
				elif c == b"BIN\x00":
					embedded_buffer = f.read(c_size)
	if dic == None:
		raise Exception("invalid glTF file")
	if "images" not in dic or not dic["images"]:
		print("Warning: no images are attached to the glTF file")
		return
	image_fn_list = []
	images = dic["images"]
	for image in images:
		if "uri" not in image:
			print("Warning: detected image with no URI")
			continue
		uri = image["uri"]
		if uri[0:5] == "data:":
			print("Warning: detected image with data URI")
			continue
		image_fn_list.append(uri.rsplit("/", maxsplit=2)[-1])

	image_fn_list = sorted(list(set(image_fn_list)))
	if image_fn_list:
		if not os.path.isdir(out_img_path):
			os.makedirs(name=out_img_path)
		for fn in image_fn_list:
			in_img_path_full = in_img_path + "/" + fn
			out_img_path_full = out_img_path + "/" + fn
			if not os.path.isfile(in_img_path_full):
				print("Warning: file " + in_img_path_full + " does not exist")
				continue
			if os.path.isfile(out_img_path_full):
				print("Warning: file " + out_img_path_full + " does exist")
				continue
			shutil.copy2(in_img_path_full, out_img_path_full, follow_symlinks=True)
	else:
		print("Warning: no images to copy")

if __name__ == "__main__":
	import argparse
	import textwrap

	parser = argparse.ArgumentParser(
		description='Copies images referenced in glTF 2.0 files.',
		usage='Use "%(prog)s --help" for more information.',
		formatter_class=argparse.RawTextHelpFormatter)
	parser.add_argument("input_file",
		type=str,
		help="The input glTF 2.0 file.")
	parser.add_argument("--input-texture-path",
		type=str,
		default="",
		help=textwrap.dedent('''\
			The path to the input directory containing texture files.
			If the path name is empty, it will default to the directory containing the input pathname.
		''')
		)
	parser.add_argument("--output-texture-path",
		type=str,
		default="",
		help=textwrap.dedent('''\
			The path to the output directory containing texture files.
			If it does not already exist, it will be created.
			If the path name is empty, it will default to the input pathname with no extension with "__textures" appended to it.
		''')
		)
	args = parser.parse_args()
	input_file = args.input_file
	if not os.path.isfile(input_file):
		raise Exception("invalid input file")
	input_file_noext = input_file.rsplit(".", maxsplit=2)[0]
	input_texture_path = args.input_texture_path
	if input_texture_path == "":
		input_texture_path = os.path.dirname(input_file)
		if input_texture_path == "":
			input_texture_path = "."
	output_texture_path = args.output_texture_path
	if output_texture_path == "":
		output_texture_path = input_file_noext + "__textures"
	gltf_copy_image(input_file, input_texture_path, output_texture_path)