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• blank transparent pngs behave like black canvas

  10 novembre 2015, par Anay Bose

  I am trying to create a scrolling image with imagemagick’s roll and crop functions. Its a frame-by—frame animation. The source image is a transparent png with some text written on it. The following code works and it creates the required frames, including some blank png images at first for a nice, smooth effect. These blank pngs are what creating problems when I am trying to convert my image frames into video with ffmpeg. FFMPEG is seemingly considering these blank pngs as black/dark images, so the resulting video contains a blackout for a few seconds in the beginning—which I do not want.

  I am using png codec with bgra pixel format. My ffmpeg command (shown below) creates smooth, clear animation with images that have some text on it.

  "ffmpeg -i trans/trans-%d.png -vcodec png -pix_fmt bgra overlay-0.mov";

  The blank pngs behave like black canvas, but as I try to write some text on them or surround them with a border (i.e. colorize in some way) the problem disappears—which seems very strange. I have tested all my images ; they are all transparent. For the past few hours, I have been searching for a solution, no luck so far. Please note those blank pngs are required in the beginning for a smooth effect, and I cannot omit them. I have uploaded a sample video in Youtube. Please note the black fade out.

  https://www.youtube.com/watch?v=Te3LuItxcDk&feature=youtu.be

  https://youtu.be/Te3LuItxcDk

  PHP code :

     $increment = 40;
  
     $count = 0; 
  
  
  
     for ($x=40; $x <= 640 ; $x+=$increment) 
  
     {
  
       $roll = new Imagick(DOCROOT . '/composite-0.png');
  
       $roll->rollImage($x, 0);
  
       $roll->writeImage(DOCROOT . '/roll/roll-' . $x . '.png');
  
  
  
      $crop = new Imagick(DOCROOT . '/roll/roll-' . $x . '.png');
  
      $crop->cropImage($x, 720, 0, 0);
  
      $crop->writeImage(DOCROOT . '/roll/crop-' . $x . '.png');
  
  
  
      $extent = new Imagick(DOCROOT . '/roll/crop-' . $x . '.png'); 
  
      # $extent->setImageBackgroundColor(new ImagickPixel('none'));
  
      $extent->setImageBackgroundColor(new ImagickPixel('transparent'));
  
      $extent->extentImage(640, $extent->getImageHeight(), 0, 0);
  
      $extent->setImageFormat('png'); 
  
      $extent->writeImage(DOCROOT . '/trans/trans-' . $count . '.png');
  
  
  
      $count++; 
  
     }

• Adding transparency to a video from black and white (and gray) alpha information video images

  3 juillet 2018, par Jan F.

  I’d like to create a video with transparency (and semi transparency) in android. The images of the source video are split into two images, the top one with color information (looks like the normal video image), the bottom one with alpha information (the same shapes but only in black and white and gray, black means transparent).

  This is the solution for iOS :
  https://medium.com/@quentinfasquel/ios-transparent-video-with-coreimage-52cfb2544d54

  What would be the best way to to this in android ?

  Can this be solved with javacv, FFmpegFrameGrabber, FFmpegFrameFilter etc.?

  Or better with OpenGL ES and shaders ?

  Are there any samples ?

  Thanks !

• FFMPEG add circular mask to videos, convert to black and white and concatenate

  3 mai 2018, par Yassine

  Hello everyone i’m a beginner and i would appreciate your help.

  I’m making a mobile application that generates custom video resumes based on the user’s videos taken from his phone, the user has to upload 5 different videos to the server from the mobile application, in the server side i want to :

  • Add a .png circular mask to each video.
  • Make each video black and white.

  • Concatenate the videos with other already existing title videos
    (e.g [userVideo1] [title1] [userVideo2] [title2]...) Visual Example

    [Edit : I would like more features]

  • Add background music
  • Add watermark logo in the middle
  • Remove silent footage from the beginning and from the end
  • Some input videos might be rotated, i want to rotate videos back to normal if they are rotated.

  So far i managed to add the circular mask, make the videos black and white and concatenate 3 videos including a premade title video, but the second user video has no sound in the output.

  This is the script i ended up with :

  ffmpeg -i uservid1.mov -i uservid2.mp4 -i mask.png -i title1.mp4  -preset 
  
  ultrafast -filter_complex "
  
  
  
  [2:v][0:v]scale2ref[s1][s2];     
  
  [s2][s1]overlay[vid1];  
  
  [2:v][1:v]scale2ref[s3][s4]; 
  
  [s4][s3]overlay[vid2];  
  
  [vid1]hue=s=0[v0]; 
  
  [vid2]hue=s=0[v1];  
  
  [v0]scale=720x400[in0]; 
  
  [v1]scale=720x400[in1]; 
  
  [3:v]scale=720x400[in3]; 
  
  [in0]setsar=sar=0[final0]; 
  
  [in1]setsar=sar=0[final1];      
  
  [in3]setsar=sar=0[final3]; 
  
  [final0][final3][final1]concat=n=3;"
  
  
  
  -codec:a copy finalCV.mp4