114 lines
3.4 KiB
Dart
114 lines
3.4 KiB
Dart
import 'dart:convert';
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import 'dart:typed_data';
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import 'package:image/image.dart' as img;
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import '../tool/encryption_util.dart';
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class SteganographyUtil {
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static const String MAGIC_HEADER = 'SGWCMAID';
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/// 图片隐写：将数据藏进图片 R 通道最低位
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static Uint8List hideDataInImage(Uint8List imageBytes, String secretData) {
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if (!secretData.startsWith(MAGIC_HEADER)) {
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throw Exception('数据格式不正确，必须以 $MAGIC_HEADER 开头');
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}
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// 1. 加密 + 压缩
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final encryptedString = EncryptionUtil.encryptAndCompress(secretData);
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// 2. 转为字节并添加 \0 结束符
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final dataBytes = utf8.encode(encryptedString);
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final payload = Uint8List(dataBytes.length + 1);
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payload.setRange(0, dataBytes.length, dataBytes);
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payload[dataBytes.length] = 0; // \0
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// 3. 解码图片
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final image = img.decodeImage(imageBytes);
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if (image == null) throw Exception('图片解码失败');
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// 4. 获取像素数据
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final imageData = image.data;
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if (imageData == null) throw Exception('图片数据为空');
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// 【关键修复】ByteBuffer 必须转换为 Uint8List 才能进行 [] 操作和获取 length
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// 注意：asUint8List() 返回的是原 buffer 的视图，修改它会直接修改 image 数据
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final Uint8List pixels = imageData.buffer.asUint8List();
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// 检查容量 (R通道只有 width * height 个字节可用)
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// pixels.length 是总字节数 (width * height * 4)
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final maxBits = pixels.length ~/ 4;
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if (payload.length * 8 > maxBits) {
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throw Exception('图片容量不足！需要 ${payload.length * 8} bits，图片仅提供 ${maxBits} bits');
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}
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// 5. 执行 LSB 隐写
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_writeLsbRChannel(pixels, payload);
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// 6. 导出 PNG
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return img.encodePng(image);
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}
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/// 从图片中提取数据
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static String? extractDataFromImage(Uint8List imageBytes) {
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final image = img.decodeImage(imageBytes);
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if (image == null) return null;
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final imageData = image.data;
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if (imageData == null) return null;
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// 【关键修复】转换为 Uint8List
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final Uint8List pixels = imageData.buffer.asUint8List();
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final List<int> extractedBytes = [];
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int currentByteValue = 0;
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int bitCount = 0;
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// 遍历像素 (RGBA, 步长 4)
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for (int i = 0; i < pixels.length; i += 4) {
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// 只取 R 通道 (index i) 的最低位
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int bit = pixels[i] & 1;
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currentByteValue = (currentByteValue << 1) | bit;
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bitCount++;
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if (bitCount == 8) {
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if (currentByteValue == 0) {
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break; // 遇到 \0 停止
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}
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extractedBytes.add(currentByteValue);
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currentByteValue = 0;
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bitCount = 0;
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}
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}
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if (extractedBytes.isEmpty) return null;
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try {
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return utf8.decode(extractedBytes);
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} catch (e) {
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return null;
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}
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}
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/// 核心写入：仅修改 R 通道
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static void _writeLsbRChannel(Uint8List pixels, Uint8List payload) {
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int payloadIndex = 0;
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int bitIndex = 0; // 0-7
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for (int i = 0; i < pixels.length; i += 4) {
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if (payloadIndex >= payload.length) break;
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int currentByte = payload[payloadIndex];
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// 取当前字节的第 bitIndex 位 (从高位到低位)
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int bit = (currentByte >> (7 - bitIndex)) & 1;
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// 修改 R 通道: 清除最低位，写入新位
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pixels[i] = (pixels[i] & 0xFE) | bit;
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bitIndex++;
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if (bitIndex > 7) {
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bitIndex = 0;
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payloadIndex++;
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}
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}
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}
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} |