问将颤动动画直接渲染到视频

EN

Future<Uint8List> _capturePngToUint8List() async {
    // renderBoxKey is the global key of my RepaintBoundary
    RenderRepaintBoundary boundary = renderBoxKey.currentContext.findRenderObject(); 
    
    // pixelratio allows you to render it at a higher resolution than the actual widget in the application.
    ui.Image image = await boundary.toImage(pixelRatio: 2.0);
    ByteData byteData = await image.toByteData(format: ui.ImageByteFormat.png);
    Uint8List pngBytes = byteData.buffer.asUint8List();

    return pngBytes;
  }

double t = 0;
int i = 1;

setState(() {
  animationController.value = 0.0;
});

Map<int, Uint8List> frames = {};
double dt = (1 / 60) / animationController.duration.inSeconds.toDouble();

while (t <= 1.0) {
  print("Rendering... ${t * 100}%");
  var bytes = await _capturePngToUint8List();
  frames[i] = bytes;

  t += dt;
  setState(() {
    animationController.value = t;
  });
  i++;
}

List<Future<File>> fileWriterFutures = [];

frames.forEach((key, value) {
  fileWriterFutures.add(_writeFile(bytes: value, location: r"D:\path\to\my\images\folder\" + "frame_$key.png"));
});

await Future.wait(fileWriterFutures);

_runFFmpeg();

Future<File> _writeFile({@required String location, @required Uint8List bytes}) async {
  File file = File(location);
  return file.writeAsBytes(bytes);
}

void _runFFmpeg() async {
  // ffmpeg -y -r 60 -start_number 1 -i frame_%d.png -c:v libx264 -preset medium -tune animation -pix_fmt yuv420p test.mp4
  var process = await Process.start(
      "ffmpeg",
      [
        "-y", // replace output file if it already exists
        "-r", "60", // framrate
        "-start_number", "1",
        "-i", r"./test/frame_%d.png", // <- Change to location of images
        "-an", // don't expect audio
        "-c:v", "libx264rgb", // H.264 encoding
        "-preset", "medium",
        "-crf",
        "10", // Ranges 0-51 indicates lossless compression to worst compression. Sane options are 0-30
        "-tune", "animation",
        "-preset", "medium",
        "-pix_fmt", "yuv420p",
        r"./test/test.mp4" // <- Change to location of output
      ],
      mode: ProcessStartMode.inheritStdio // This mode causes some issues at times, so just remove it if it doesn't work. I use it mostly to debug the ffmpeg process' output
   );

  print("Done Rendering");
}

final FlutterFFmpeg _flutterFFmpeg =
    new FlutterFFmpeg(); // Create new ffmpeg instance somewhere in your code

// Function to create the video. All png files must be available in your target location prior to calling this function.
Future<String> _createVideoFromPngFiles(String location, int framerate) async {
  final dateAsString = DateFormat('ddMMyyyy_hhmmss').format(DateTime.now());
  final filePath =
      "$location/video_$dateAsString.mov"; // had to use mov to be able to play the video on QuickTime

  var arguments = [
    "-y", // Replace output file if it already exists
    "-r", "$framerate", // Your target framerate
    "-start_number", "1",
    "-i",
    "$location/frame_%d.png", // The location where you saved all your png files
    "-an", // Don't expect audio
    "-c:v",
    "libx264", // H.264 encoding, make sure to use the full-gpl ffmpeg package version
    "-preset", "medium",
    "-crf",
    "10", // Ranges 0-51 indicates lossless compression to worst compression. Sane options are 0-30
    "-tune", "animation",
    "-preset", "medium",
    "-pix_fmt",
    "yuv420p", // Set the pixel format to make it compatible for QuickTime
    "-vf",
    "pad=ceil(iw/2)*2:ceil(ih/2)*2", // Make sure that height and width are divisible by 2
    filePath
  ];

  final result = await _flutterFFmpeg.executeWithArguments(arguments);
  return result == 0
      ? filePath
      : ''; // Result == 0 indicates that video creation was successful
}