Convert glTF images to ktx using https://github.com/cdwfs/img2ktx

convert_gltf_ktx.py

import json
import argparse
import sys
import os
import subprocess

parser = argparse.ArgumentParser(description='Convert a glTF file textures to the ktx format')
parser.add_argument('--input', type=str, help='glTF file')
parser.add_argument('--output', type=str, help='Filename for updated glTF file')
parser.add_argument('--format', type=str, help='KTX format')
args = parser.parse_args()

if args.input == None:
    sys.exit("No input file specified")

if args.input != None:
    output_format = args.format
else:
    output_format = "RGBA"

input_file = args.input

output_file = ""
if args.output != None:
    output_file = args.output

if not os.path.isfile(input_file):
    sys.exit("File does not exist")

with open(input_file) as json_file:
    data = json.load(json_file)
    for image in data['images']:

        input_image_file = image['uri']
        output_image_file = os.path.splitext(input_image_file)[0] + ".ktx"

        if os.path.isfile(input_image_file):
            print("Converting %s" % input_image_file)
            subprocess.check_output([
                "img2ktx",
                "-f", output_format,
                "-m",
                "-o", output_image_file,
                input_image_file
            ])

        image['uri'] = output_image_file            

if output_file != "":
    with open(output_file, 'w') as outfile:
        json.dump(data, outfile)