while True: chunk_type, data, crc = read_chunk(fin) if chunk_type == CHUNK_TYPE_MPNG: idx = struct.unpack('>I', data[:4])[0] if replace_map and idx in replace_map: new_compressed = replace_map[idx] else: # Find matching stream and reflate for stored_idx, comp in streams: if stored_idx == idx: new_compressed = reflate_stream(comp, recompress_level) break else: new_compressed = data[4:] # unchanged new_data = struct.pack('>I', idx) + new_compressed write_chunk(fout, CHUNK_TYPE_MPNG, new_data) else: # Copy other chunks unchanged fout.write(struct.pack('>I', len(data))) fout.write(chunk_type) fout.write(data) fout.write(struct.pack('>I', crc))
xtool -mpng+reflate appears to be a command-line option for a tool called xtool , which is likely used for image processing or conversion. Let's dive deeper into what this command might do. xtool -mpng+reflate
def write_chunk(f, chunk_type, data): """Write PNG chunk with CRC""" f.write(struct.pack('>I', len(data))) f.write(chunk_type) f.write(data) crc = zlib.crc32(chunk_type + data) & 0xffffffff f.write(struct.pack('>I', crc)) while True: chunk_type, data, crc = read_chunk(fin) if
if extract_only: for idx, comp in streams: raw = zlib.decompress(comp) out_file = f"{Path(input_png).stem}_stream_{idx}.raw" Path(out_file).write_bytes(raw) print(f"Extracted stream {idx} to {out_file}") return while True: chunk_type