Reduce app size

lib/utils/pdf.dart

@@ -1,33 +1,28 @@
+import 'dart:async';
+import 'dart:convert';
 import 'dart:isolate';
-
-import 'package:pdf/widgets.dart';
+import 'package:venera/foundation/app.dart';
 import 'package:venera/foundation/local.dart';
+import 'package:venera/utils/image.dart';
 import 'package:venera/utils/io.dart';
+import 'package:zip_flutter/zip_flutter.dart';
+
+typedef DecodeImage = Future<Image> Function(Uint8List data);
 
 Future<void> _createPdfFromComic({
   required LocalComic comic,
   required String savePath,
   required String localPath,
+  required DecodeImage decodeImage,
 }) async {
-  final pdf = Document(
-    title: comic.title,
-    author: comic.subTitle ?? "",
-    producer: "Venera",
-  );
-
-  pdf.document.outline;
+  var images = <String>[];
 
   var baseDir = comic.directory.contains('/') || comic.directory.contains('\\')
       ? comic.directory
       : FilePath.join(localPath, comic.directory);
 
   // add cover
-  var imageData = File(FilePath.join(baseDir, comic.cover)).readAsBytesSync();
-  pdf.addPage(Page(
-    build: (Context context) {
-      return Image(MemoryImage(imageData), fit: BoxFit.contain);
-    },
-  ));
+  images.add(FilePath.join(baseDir, comic.cover));
 
   bool multiChapters = comic.chapters != null;
 
@@ -51,42 +46,360 @@ Future<void> _createPdfFromComic({
     reorderFiles(files);
 
     for (var file in files) {
-      var imageData = (file as File).readAsBytesSync();
-      pdf.addPage(Page(
-        build: (Context context) {
-          return Image(MemoryImage(imageData), fit: BoxFit.contain);
-        },
-      ));
+      images.add(file.path);
     }
   } else {
     for (var chapter in comic.chapters!.keys) {
       var files = Directory(FilePath.join(baseDir, chapter)).listSync();
       reorderFiles(files);
       for (var file in files) {
-        var imageData = (file as File).readAsBytesSync();
-        pdf.addPage(Page(
-          build: (Context context) {
-            return Image(MemoryImage(imageData), fit: BoxFit.contain);
-          },
-        ));
+        images.add(file.path);
       }
     }
   }
 
-  final file = File(savePath);
-  file.writeAsBytesSync(await pdf.save());
+  var generator = PdfGenerator(
+    title: comic.title,
+    author: comic.subtitle,
+    imagePaths: images,
+    outputPath: savePath,
+    decodeImage: decodeImage,
+  );
+  await generator.generate();
+}
+
+Future<Isolate> _runIsolate(
+    LocalComic comic, String savePath, SendPort sendPort) {
+  var localPath = LocalManager().path;
+  return Isolate.spawn<SendPort>(
+    (sendPort) => overrideIO(
+      () async {
+        var receivePort = ReceivePort();
+        sendPort.send(receivePort.sendPort);
+
+        Completer<Image>? completer;
+
+        Future<Image> decodeImage(Uint8List data) async {
+          if (completer != null) {
+            throw Exception('Another image is being decoded');
+          }
+          sendPort.send(data);
+          completer = Completer();
+          return completer!.future;
+        }
+
+        receivePort.listen((message) {
+          if (message is Image) {
+            if (completer == null) {
+              throw Exception('No image is being decoded');
+            }
+            completer!.complete(message);
+            completer = null;
+          }
+        });
+
+        await _createPdfFromComic(
+          comic: comic,
+          savePath: savePath,
+          localPath: localPath,
+          decodeImage: decodeImage,
+        );
+
+        sendPort.send(null);
+      },
+    ),
+    sendPort,
+  );
 }
 
 Future<void> createPdfFromComicIsolate({
   required LocalComic comic,
   required String savePath,
 }) async {
-  var localPath = LocalManager().path;
-  return Isolate.run(() => overrideIO(() async {
-        return await _createPdfFromComic(
-          comic: comic,
-          savePath: savePath,
-          localPath: localPath,
-        );
-      }));
+  var receivePort = ReceivePort();
+  SendPort? sendPort;
+  Isolate? isolate;
+  var completer = Completer<void>();
+  receivePort.listen((message) {
+    if (message is SendPort) {
+      sendPort = message;
+    } else if (message is Uint8List) {
+      Image.decodeImage(message).then((image) {
+        sendPort!.send(image);
+      });
+    } else if (message == null) {
+      receivePort.close();
+      completer.complete();
+      isolate!.kill();
+    }
+  });
+  isolate = await _runIsolate(comic, savePath, receivePort.sendPort);
+  return completer.future;
+}
+
+class PdfGenerator {
+  final String title;
+  final String author;
+  final List<String> imagePaths;
+  final String outputPath;
+  final DecodeImage decodeImage;
+
+  // PDF文件的对象ID计数器
+  int _objectId = 1;
+
+  // 存储每个对象在PDF中的字节位置
+  final Map<int, int> _objectOffsets = {};
+
+  static const double a4Width = 595.0; // points
+  static const double a4Height = 842.0; // points
+
+  PdfGenerator({
+    required this.title,
+    required this.author,
+    required this.imagePaths,
+    required this.outputPath,
+    required this.decodeImage,
+  });
+
+  Future<void> generate() async {
+    var file = File(outputPath);
+    final output = file.openWrite();
+
+    int length = 0;
+
+    void write(String str) {
+      var data = utf8.encode(str);
+      output.add(data);
+      length += data.length;
+    }
+
+    void writeData(Uint8List data) {
+      output.add(data);
+      length += data.length;
+    }
+
+    int getCurrentLength() {
+      return length;
+    }
+
+    // 1. 写入PDF头部
+    write('%PDF-1.7\n%\xFF\xFF\xFF\xFF\n\n');
+
+    // 2. 写入Catalog对象
+    _objectOffsets[_objectId] = getCurrentLength();
+    write('$_objectId 0 obj\n');
+    write('<<\n');
+    write('/Type /Catalog\n');
+    write('/Pages ${_objectId + 1} 0 R\n');
+    write('>>\nendobj\n\n');
+
+    final catalogId = _objectId++;
+
+    // 3. 写入Pages对象
+    _objectOffsets[_objectId] = getCurrentLength();
+    write('$_objectId 0 obj\n');
+    write('<<\n');
+    write('/Type /Pages\n');
+    write('/Kids [');
+    final pageIds = <int>[];
+    for (var i = 0; i < imagePaths.length; i++) {
+      pageIds.add(_objectId + 1 + i * 3);
+      write('${_objectId + 1 + i * 3} 0 R ');
+    }
+    write(']\n');
+    write('/Count ${imagePaths.length}\n');
+    write('>>\nendobj\n\n');
+
+    final pagesId = _objectId++;
+
+    // 4. 为每个图片创建Page和Image对象
+    for (var i = 0; i < imagePaths.length; i++) {
+      final imagePath = imagePaths[i];
+      final image = await _getImage(imagePath);
+
+      // 写入Page对象
+      _objectOffsets[_objectId] = getCurrentLength();
+      write('$_objectId 0 obj\n');
+      write('<<\n');
+      write('/Type /Page\n');
+      write('/Parent $pagesId 0 R\n');
+      write('/Resources <<\n');
+      write('/XObject << /Im${i + 1} ${_objectId + 1} 0 R >>\n');
+      write('>>\n');
+      write('/MediaBox [0 0 $a4Width $a4Height]\n');
+      write('/Contents ${_objectId + 2} 0 R\n');
+      write('>>\nendobj\n\n');
+
+      _objectId++;
+
+      // 写入Image对象
+      _objectOffsets[_objectId] = getCurrentLength();
+      write('$_objectId 0 obj\n');
+      write('<<\n');
+      write('/Type /XObject\n');
+      write('/Subtype /Image\n');
+      write('/Width ${image.width}\n');
+      write('/Height ${image.height}\n');
+      write('/ColorSpace /DeviceRGB\n');
+      write('/BitsPerComponent 8\n');
+      write('/Filter /FlateDecode\n');
+      write('/Length ${image.data.length}\n');
+      write('>>\nstream\n');
+      writeData(image.data);
+      write('\nendstream\nendobj\n\n');
+
+      _objectId++;
+
+      // 写入Contents对象（绘制图片的指令）
+      _objectOffsets[_objectId] = getCurrentLength();
+      write('$_objectId 0 obj\n');
+      write('<<\n');
+      var stream = '';
+      stream += 'q\n';
+      // Calculate scaling factors
+      var scaleX = a4Width / image.width;
+      var scaleY = a4Height / image.height;
+      var scale = scaleX < scaleY ? scaleX : scaleY;
+      // Calculate centering offsets
+      var offsetX = (a4Width - (image.width * scale)) / 2;
+      var offsetY = (a4Height - (image.height * scale)) / 2;
+      // Apply transformation matrix
+      stream += '1 0 0 1 $offsetX $offsetY cm\n'; // Translate
+      stream += '${scale * image.width} 0 0 ${scale * image.height} 0 0 cm\n';
+      stream += '/Im${i + 1} Do\n';
+      stream += 'Q\n';
+      var streamData = utf8.encode(stream);
+      write('/Length ${streamData.length}\n');
+      write('>>\nstream\n');
+      writeData(streamData);
+      write('endstream\nendobj\n\n');
+
+      _objectId++;
+    }
+
+    // 5. 写入Info对象（元数据）
+    final infoId = _objectId;
+    _objectOffsets[_objectId] = getCurrentLength();
+    write('$_objectId 0 obj\n');
+    write('<<\n');
+    write('/Title <');
+    writeData(_toPdfString(title));
+    write('>\n');
+    write('/Author <');
+    writeData(_toPdfString(author));
+    write('>\n');
+    write('/Producer (venera v${App.version})\n');
+    write('/CreationDate (D:${_formatDateTime(DateTime.now())})\n');
+    write('>>\nendobj\n\n');
+
+    _objectId++;
+
+    // 6. 写入交叉引用表
+    final xrefOffset = getCurrentLength();
+    write('xref\n');
+    write('0 $_objectId\n');
+    write('0000000000 65535 f\r\n');
+
+    for (var i = 1; i < _objectId; i++) {
+      final offset = _objectOffsets[i]!;
+      write('${offset.toString().padLeft(10, '0')} 00000 n\r\n'); // 使用\r\n
+    }
+
+    // 7. 写入文件尾部
+    write('trailer\n');
+    write('<<\n');
+    write('/Size $_objectId\n');
+    write('/Root $catalogId 0 R\n');
+    write('/Info $infoId 0 R\n');
+    write('>>\n');
+    write('startxref\n');
+    write('$xrefOffset\n');
+    write('%%EOF\n');
+
+    await output.close();
+  }
+
+  int _codeUnitForDigit(int digit) =>
+      digit < 10 ? digit + 0x30 : digit + 0x61 - 10;
+
+  Uint8List _toPdfString(String str) {
+    Uint8List data;
+    try {
+      data = latin1.encode(str);
+    } catch (e) {
+      data = Uint8List.fromList(<int>[0xfe, 0xff] + _encodeUtf16be(str));
+    }
+    var result = <int>[];
+    for (final byte in data) {
+      result.add(_codeUnitForDigit((byte & 0xF0) >> 4));
+      result.add(_codeUnitForDigit(byte & 0x0F));
+    }
+    return Uint8List.fromList(result);
+  }
+
+  List<int> _encodeUtf16be(String str) {
+    const unicodeReplacementCharacterCodePoint = 0xfffd;
+    const unicodeByteZeroMask = 0xff;
+    const unicodeByteOneMask = 0xff00;
+    const unicodeValidRangeMax = 0x10ffff;
+    const unicodePlaneOneMax = 0xffff;
+    const unicodeUtf16ReservedLo = 0xd800;
+    const unicodeUtf16ReservedHi = 0xdfff;
+    const unicodeUtf16Offset = 0x10000;
+    const unicodeUtf16SurrogateUnit0Base = 0xd800;
+    const unicodeUtf16SurrogateUnit1Base = 0xdc00;
+    const unicodeUtf16HiMask = 0xffc00;
+    const unicodeUtf16LoMask = 0x3ff;
+
+    final encoding = <int>[];
+
+    void add(int unit) {
+      encoding.add((unit & unicodeByteOneMask) >> 8);
+      encoding.add(unit & unicodeByteZeroMask);
+    }
+
+    for (final unit in str.codeUnits) {
+      if ((unit >= 0 && unit < unicodeUtf16ReservedLo) ||
+          (unit > unicodeUtf16ReservedHi && unit <= unicodePlaneOneMax)) {
+        add(unit);
+      } else if (unit > unicodePlaneOneMax && unit <= unicodeValidRangeMax) {
+        final base = unit - unicodeUtf16Offset;
+        add(unicodeUtf16SurrogateUnit0Base +
+            ((base & unicodeUtf16HiMask) >> 10));
+        add(unicodeUtf16SurrogateUnit1Base + (base & unicodeUtf16LoMask));
+      } else {
+        add(unicodeReplacementCharacterCodePoint);
+      }
+    }
+    return encoding;
+  }
+
+  // 格式化日期时间
+  String _formatDateTime(DateTime dt) {
+    return dt
+        .toUtc()
+        .toString()
+        .replaceAll('-', '')
+        .replaceAll(':', '')
+        .replaceAll(' ', '')
+        .replaceAll('.', '')
+        .substring(0, 14);
+  }
+
+  Future<({int width, int height, Uint8List data})> _getImage(
+      String imagePath) async {
+    var data = await File(imagePath).readAsBytes();
+    var image = await decodeImage(data);
+    var width = image.width;
+    var height = image.height;
+    data = Uint8List(width * height * 3);
+    for (var i = 0; i < width * height; i++) {
+      var pixel = image.getPixelAtIndex(i); // RGBA
+      data[i * 3] = pixel & 0xFF; // R
+      data[i * 3 + 1] = (pixel >> 8) & 0xFF; // G
+      data[i * 3 + 2] = (pixel >> 16) & 0xFF; // B
+    }
+    data = tdeflCompressData(data, true, true, 9);
+    return (width: width, height: height, data: data);
+  }
 }