imgparser.py

#!/usr/bin/python3

import sys

#
# NBA Jam/Midway IMG format parser
# https://github.com/historicalsource/nba-jam
#
if __name__ == '__main__':

    filename = sys.argv[1]

    with open(filename, "rb") as fp:
        print('=================')
        print('image information')
        print('=================')
        # total images in file
        num_images = int.from_bytes(fp.read(1), 'little')
        print('total images: ',num_images)

        # img list pointer
        fp.seek(4)
        file_list_offset = bytearray(fp.read(4))

        # we need to reverse the order (little endian)
        offset = int.from_bytes(file_list_offset, byteorder='little')
        fp.seek(offset)

        # for each of the images, read 50 bytes to retrieve file names
        while num_images > 0:
            # print(hex(fp.tell()))
            image_metadata = fp.read(50)
            file_name_length = image_metadata.find(b'\00')
            print(image_metadata[0:file_name_length].decode('utf-8'))
            num_images -= 1

        # palette metadata is stored right after the image metadata
        # in blocks of 26 bytes with the same delimiter on offset[25]
        print('===================')
        print('palette information')
        print('===================')
        palette_metadata = fp.read(26)
        delimiter = palette_metadata[25]
        while True:
            # print(hex(fp.tell()))
            if len(palette_metadata) == 26:
                if palette_metadata[25] == delimiter:
                    palette_name_length = palette_metadata.find(b'\00')
                    print(palette_metadata[0:palette_name_length].decode('utf-8'))
                    palette_offset = int.from_bytes(palette_metadata[14:18], byteorder='little')
                    print('offset: ', hex(palette_offset))
                    palette_metadata = fp.read(26)
                else:
                    break
            else:
                break

Palette LGMDRED2 on offset 0x59c: