LSB 输出流，按顺序将数据位嵌入图像各像素通道的最低有效位。
| 9 | |
| 10 | |
| 11 | class LSBOutputStream: |
| 12 | """LSB 输出流，按顺序将数据位嵌入图像各像素通道的最低有效位。""" |
| 13 | |
| 14 | def __init__(self, image: Image.Image, data_length: int, |
| 15 | filename: str, config: LSBConfig): |
| 16 | self.image = image.copy() |
| 17 | self.config = config |
| 18 | self.header = LSBDataHeader(data_length, config.get_max_bits_used_per_channel(), |
| 19 | filename, config) |
| 20 | |
| 21 | self.pixels = np.array(self.image) |
| 22 | self.height, self.width, self.channels = self.pixels.shape |
| 23 | |
| 24 | bits_per_pixel = self.channels * config.get_max_bits_used_per_channel() |
| 25 | total_bits = (len(self.header.to_bytes()) + data_length) * 8 |
| 26 | if (total_bits + bits_per_pixel - 1) // bits_per_pixel > self.width * self.height: |
| 27 | raise ValueError(f"图像太小，无法嵌入 {data_length} 字节的数据") |
| 28 | |
| 29 | self._buffer = bytearray(self.header.to_bytes()) |
| 30 | |
| 31 | def write(self, data: bytes): |
| 32 | self._buffer.extend(data) |
| 33 | |
| 34 | def flush(self): |
| 35 | self._embed(bytes(self._buffer)) |
| 36 | self.image = Image.fromarray(np.clip(self.pixels, 0, 255).astype(np.uint8)) |
| 37 | |
| 38 | def _embed(self, data: bytes): |
| 39 | bits_per_ch = self.config.get_max_bits_used_per_channel() |
| 40 | bits = np.unpackbits(np.frombuffer(data, dtype=np.uint8)) |
| 41 | n = len(bits) |
| 42 | |
| 43 | if bits_per_ch == 1: |
| 44 | # 顺序 LSB：flat_idx == position，直接切片，避免 fancy indexing |
| 45 | flat = self.pixels.reshape(-1) |
| 46 | flat[:n] = ((flat[:n].astype(np.int32) & 0xFE) | bits).astype(np.uint8) |
| 47 | else: |
| 48 | for i, bit in enumerate(bits): |
| 49 | ch_pos = i // bits_per_ch |
| 50 | bit_slot = i % bits_per_ch |
| 51 | pixel_idx = ch_pos // self.channels |
| 52 | channel = ch_pos % self.channels |
| 53 | row = pixel_idx // self.width |
| 54 | col = pixel_idx % self.width |
| 55 | v = int(self.pixels[row, col, channel]) |
| 56 | mask = 0xFF ^ (1 << bit_slot) |
| 57 | self.pixels[row, col, channel] = (v & mask) | (int(bit) << bit_slot) |
| 58 | |
| 59 | def get_image(self) -> Image.Image: |
| 60 | return self.image |