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• In Flutter, how to get image pixel

  12 janvier 2024, par Pianone

  my code here

  


  var response = await Dio().get(
   url,
   options: Options(responseType: ResponseType.bytes)
);
Uint8List? srcImage = Uint8List.fromList(response.data);
Uint8List? watermark = await captureWaterMark();
Image i = Image.memory(srcImage!);
//how can I get the pixel (Image i) such like 1920*1080 or just width/hight pixel
...tell me how to do...
srcImage = await addWaterMarkByFfmpegCommand(srcImage, watermark);
   final result = await ImageGallerySaver.saveImage(
      srcImage!, name: name,
   );


  


  i need get the pic pixel so that i can use it in ffmpeg command, it a func that add a watermark into srcImage, but cause their pixel ratio too diff to adapted watermark

  


  i try to get pixel from ffmpeg... but i failed

  


  /// addWaterMark by using ffmpeg Command
Future addWaterMarkByFfmpegCommand(Uint8List srcImg, Uint8List watermark) async {
  try {
    final Directory tempDir = await Directory.systemTemp.createTemp();
    final File image1File = File('${tempDir.path}/srcImg.jpg');
    await image1File.writeAsBytes(srcImg);
    final File image2File = File('${tempDir.path}/watermark.png');
    await image2File.writeAsBytes(watermark);

    final String outputFilePath = '${tempDir.path}/output.jpg';
    //when i get srcImage pixel, the positions in bold(iw*1) in the following commands will be replaced to make watermark adapted
    final String command =
        '-i ${image1File.path} -i ${image2File.path} -filter_complex "[1:v]scale=**iw*1**:-1[v1];[0:v][v1]overlay=10:10" -frames:v 1 $outputFilePath';
    await FFmpegKit.execute(command);

    final File outputFile = File(outputFilePath);
    final Uint8List outputBytes = await outputFile.readAsBytes();
    return outputBytes;
  } catch (e) {
    print('Error executing ffmpeg command: $e');
  }
  return null;
}


  


  ps : i am new to flutter and ffmpeg, plz help me, I'd appreciate, thanks alot

  


• ffmpeg cut video and burn subtitle in a single command

  3 janvier 2020, par razvan

  I want to cut a piece out of a video and burn subtitle in that piece.

  I can do this in 3 steps :

  1. cut the video
     ffmpeg -ss 25:00 -to 26:00 -i vid.mp4 -c copy out.mp4

  2. cut the subtitle
     ffmpeg -i sub.srt -ss 25:00 -to 26:00 out.srt

  3. burn subtitle in the video piece
     ffmpeg -i out.mp4  -vf subtitles=out.srt  -c:a copy -y final.mp4

  But I want to do this in a single ffmpeg command.

  If I do this
  ffmpeg -ss 25:00 -to 26:00 -i vid.mp4   -vf subtitles=sub.srt  -c:a copy -y final.mp4
  the video is cut but no subtitle is burned into it.
  This is fast.

  If I do this
  ffmpeg  -i vid.mp4  -ss 25:00 -to 26:00 -vf subtitles=sub.srt  -c:a copy -y final.mp4
  the video is cut and subtitles burned correctly,but there is a delay in starting writing the final.mp4.
  I think ffmpeg is processing vid.mp4 from the beginning till it reach the -ss time (and drop that part)
  then continue processing and writing it to final.mp4

  Is there a way to do this fast and in a single ffmpeg command ?
  Like ffmpeg going directly to -ss time and cut that, process it, burn subtitle in it.

  Thanks

• ffmpeg join multiple audio with acrossfade filter

  30 avril 2017, par alditis

  I have audio file multiple :

  001.ogg, 002.ogg, ..., 100.ogg

  I need join the files with overfade filter between they.

  I did it two in two a cumulative way :

  ffmpeg -i 001.ogg -i 002.ogg -filter_complex acrossfade=d=3:o=1:c1=tri:c2=tri -b:a 128k -o r01.ogg
  
  ffmpeg -i r01.ogg -i 003.ogg -filter_complex acrossfade=d=3:o=1:c1=tri:c2=tri -b:a 128k -o r02.ogg
  
  ffmpeg -i r02.ogg -i 004.ogg -filter_complex acrossfade=d=3:o=1:c1=tri:c2=tri -b:a 128k -o r02.ogg
  
  
  
  ....
  
  ffmpeg -i r98.ogg -i 100.ogg -filter_complex acrossfade=d=3:o=1:c1=tri:c2=tri -b:a 128k -o final.ogg

  But final.ogg does not have good sound on the firsts songs (less quality while more cumulative).

  How can I avoid less quality in the final.ogg ?

  Other way is concat but : How do you define the filter acrossfade using concat ?

  ffmpeg -i "concat:1.ogg|2.ogg|...|100.ogg" copy final.ogg