tool.py

# based on https://github.com/xdanieldzd/Scarlet/blob/master/Scarlet.IO.ImageFormats/SHTXFS.cs

import datetime
from sys import argv, exit

from PIL import Image

def log(s):
    print("[{}] {}".format(datetime.datetime.now(), s))


def shtx_to_png(in_path, out_path):
    fin = open(in_path, "rb")

    tag = fin.read(6)
    width = int.from_bytes(fin.read(2), byteorder="little")
    height = int.from_bytes(fin.read(2), byteorder="little")
    unk = fin.read(2)

    log("Converting...")

    palette = []
    for x in range(256):
        palette.append(int.from_bytes(fin.read(4), byteorder="little"))

    im = Image.new("RGBA", (width, height))
    pixels = im.load()

    for y in range(height):
        for x in range(width):
            pixel = palette[ord(fin.read(1))]
            pixels[(x, y)] = (pixel & 0xFF, (pixel & 0xFF00) >> 8, (pixel & 0xFF0000) >> 16, (pixel & 0xFF000000) >> 24)

    fin.close()

    im.save(out_path)

    log("Saved {}".format(out_path))


def png_to_shtx(orig_path, in_path, out_path):
    fin = open(orig_path, "rb")
    fin.seek(0xA)
    magic = fin.read(2)
    log("Reusing magic 0x{:x}".format(int.from_bytes(magic, byteorder="little")))
    fin.close()

    im = Image.open(in_path)
    width, height = im.size
    pixels = im.load()

    log("Building the palette...")
    colors = set()

    for y in range(height):
        for x in range(width):
            p = pixels[(x, y)]
            color = p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24)
            colors.add(color)

    if len(colors) > 256:
        log("Error: palette is too big. Make sure your image only contains 256 different colors. (Use pngquant)")
        return -1

    color_to_idx = dict()
    palette = []
    for color in colors:
        color_to_idx[color] = len(palette)
        palette.append(color)

    log("Writing the image...")

    fout = open(out_path, "wb")
    fout.write(b"SHTXFS")
    fout.write(width.to_bytes(2, byteorder="little"))
    fout.write(height.to_bytes(2, byteorder="little"))
    fout.write(magic)

    for color in palette:
        fout.write(color.to_bytes(4, byteorder="little"))

    for y in range(height):
        for x in range(width):
            p = pixels[(x, y)]
            color = p[0] | (p[1] << 8) | (p[2] << 16) | (p[3] << 24)
            fout.write(color_to_idx[color].to_bytes(1, byteorder="little"))
    fout.close()

    log("Saved {}".format(out_path))


def main():
    if len(argv) == 3:
        return shtx_to_png(argv[1], argv[2])
    elif len(argv) == 4:
        return png_to_shtx(argv[1], argv[2], argv[3])
    else:
        print("Usage:")
        print("\tConvert shtx to png:")
        print("\t\tpython tool.py source.shtx output.png")
        print("\tConvert png to shtx:")
        print("\t\tpython tool.py original.shtx source.png output.shtx")
        return -1


if __name__ == "__main__":
    exit(main())