104 lines
3.0 KiB
Dart
104 lines
3.0 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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class SteganographyUtil {
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static const String MAGIC_HEADER = 'SGWCMAID';
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/// 图片隐写：写入数据
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static Uint8List hideDataInImage(Uint8List imageBytes, String secretData) {
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// 1. 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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// 2. 准备数据：必须以 MAGIC_HEADER 开头，并以 \0 结尾
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final dataBytes = utf8.encode(secretData);
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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; // 终止符
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// 检查容量
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if (payload.length * 8 > image.width * image.height) {
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throw Exception('图片像素不足以容纳数据');
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}
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int payloadIndex = 0;
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int bitIndex = 7; // MSB First (最高位优先)
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// ✅ 修复：必须严格按照 Java 的 (y, x) 顺序遍历，确保坐标对齐
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bool finished = false;
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for (int y = 0; y < image.height; y++) {
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for (int x = 0; x < image.width; x++) {
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if (payloadIndex >= payload.length) {
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finished = true;
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break;
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}
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// 获取当前坐标的像素
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final pixel = image.getPixel(x, y);
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// 取出当前字节的特定位
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int currentByte = payload[payloadIndex];
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int bit = (currentByte >> bitIndex) & 1;
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// ✅ 修复：通过 red 分量操作，屏蔽不同图片格式（RGBA/BGRA）的底层差异
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int r = pixel.r.toInt();
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int g = pixel.g.toInt();
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int b = pixel.b.toInt();
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int a = pixel.a.toInt();
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// 修改 R 通道最低位
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r = (r & 0xFE) | bit;
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// 写回像素（保持其他通道不变）
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image.setPixel(x, y, img.ColorRgba8(r, g, b, a));
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bitIndex--;
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if (bitIndex < 0) {
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bitIndex = 7;
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payloadIndex++;
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}
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}
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if (finished) break;
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}
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// ✅ 必须导出为 PNG，防止 JPEG 压缩破坏 LSB 位
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return Uint8List.fromList(img.encodePng(image));
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}
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/// 提取数据（本地调试用，逻辑需与写入完全对称）
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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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List<int> extractedBytes = [];
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int currentByte = 0;
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int bitCount = 0;
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outer:
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for (int y = 0; y < image.height; y++) {
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for (int x = 0; x < image.width; x++) {
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final pixel = image.getPixel(x, y);
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int bit = pixel.r.toInt() & 1;
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// MSB First 组装字节
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currentByte = (currentByte << 1) | bit;
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bitCount++;
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if (bitCount == 8) {
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if (currentByte == 0) break outer; // 结束符
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extractedBytes.add(currentByte);
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currentByte = 0;
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bitCount = 0;
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}
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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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} |