generate LVGL 9 binary

Signed-off-by: Peter Siegmund <developer@mars3142.org>

server/cinema/lib/common/lvgl_image_converter.dart

@@ -0,0 +1,68 @@
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:image/image.dart' as img;
+import 'package:injectable/injectable.dart';
+
+import 'image_resizer.dart';
+
+@singleton
+class LvglImageConverter {
+  final ImageResizer _imageResizer;
+
+  LvglImageConverter(this._imageResizer);
+  static const int _magic = 0x19;
+  static const int _colorFormatRgb565 = 0x12;
+  static const int _flags = 0x00;
+
+  int _toRgb565(int r, int g, int b) {
+    return ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | (b >> 3);
+  }
+
+  Future<void> convertPngToBin(String imagePath, String binPath) async {
+    final imageFile = File(imagePath);
+    if (!await imageFile.exists()) {
+      throw FileSystemException('Image file not found', imagePath);
+    }
+
+    final bytes = await imageFile.readAsBytes();
+    var image = img.decodeImage(bytes);
+    if (image == null) {
+      throw FormatException('Failed to decode image: $imagePath');
+    }
+
+    image = _imageResizer.resizeToFit(image);
+
+    final w = image.width;
+    final h = image.height;
+    final stride = (w * 16 + 7) ~/ 8;
+
+    final header = ByteData(12);
+    header.setUint8(0, _magic);
+    header.setUint8(1, _colorFormatRgb565);
+    header.setUint16(2, _flags, Endian.little);
+    header.setUint16(4, w, Endian.little);
+    header.setUint16(6, h, Endian.little);
+    header.setUint16(8, stride, Endian.little);
+    header.setUint16(10, 0, Endian.little); // reserved
+
+    final body = ByteData(w * h * 2);
+    var offset = 0;
+    for (var y = 0; y < h; y++) {
+      for (var x = 0; x < w; x++) {
+        final pixel = image.getPixel(x, y);
+        final rgb565 = _toRgb565(pixel.r.toInt(), pixel.g.toInt(), pixel.b.toInt());
+        body.setUint16(offset, rgb565, Endian.little);
+        offset += 2;
+      }
+    }
+
+    final binFile = File(binPath);
+    await binFile.parent.create(recursive: true);
+    await binFile.writeAsBytes([
+      ...header.buffer.asUint8List(),
+      ...body.buffer.asUint8List(),
+    ]);
+  }
+}
+