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• avfilter/scale_eval : Reduce rounding error.

  26 septembre 2022, par Tristan Schmelcher

  avfilter/scale_eval : Reduce rounding error.
  When force_original_aspect_ratio and force_divisible_by are both
  
  used, dimensions are now rounded to the nearest allowed multiple of
  
  force_divisible_by rather than first rounding to the nearest integer and
  
  then rounding in a static direction. This results in less distortion of
  
  the aspect ratio.
  Reviewed-by : Thierry Foucu <tfoucu@google.com>
  
  Signed-off-by : Tristan Schmelcher <tschmelcher@google.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/scale_eval.c
  • [DH] libavfilter/scale_eval.h

• Implementing picture zoom effect using Rmagick and FFmpeg

  26 juin 2013, par DenisKo

  I have a picture and I need to get zoom effect on the resulting video. I almost get the desired result.. but. The resulting picture looks a bit shaky. It's because of rounding on cropping and resizing.. so centre of the picture shifts slightly with each conversion. What can i do with that ? Or maybe there is some other method to implement it ?
  In the input I have
  picture,zoom_type,zoom_percent,zoom_duration,scene_duration
  Here is part of the code which making the job :

  img = Magick::ImageList.new(picture).first
  
  width, height = img.columns.to_f, img.rows.to_f
  
  img_fps = 30
  
  if width >= height
  
    aspect_ratio = (width / height)
  
    zoom_small_size = ((height * (100 - zoom_percent)) / 100).to_f
  
    small_size = height
  
  else
  
    aspect_ratio = (height / width)
  
    zoom_small_size = ((width * (100 - zoom_percent)) / 100).to_f
  
    small_size = width
  
  end
  
  factor = (((small_size - zoom_small_size) / (img_fps * zoom_duration))).to_f
  
  while factor < 2
  
    img_fps -= 1
  
    factor = ((small_size - zoom_small_size) / (img_fps * zoom_duration))
  
  end
  
  total_images = img_fps * scene_duration
  
  zoom_images = img_fps * zoom_duration_seed
  
  new_width =  width
  
  new_height =  height
  
  zoom_changed_small_size = small_size
  
  
  
  total_images.times do |i|
  
  if zoom_images > 0 && zoom_changed_small_size > zoom_small_size
  
    img_n = img.crop(new_width, new_height, true)
  
    new_width = (width <= height) ? (new_width - factor).round : (new_width-factor*aspect_ratio).round
  
    new_height = (width >= height) ? (new_height-factor).round : (new_height-factor*aspect_ratio).round
  
    zoom_changed_small_size = (width >= height) ? img_n.rows : img_n.columns
  
    img_n.resize_to_fill!(width, height)
  
    img_n.write("#{sprintf("img_%04d.jpg" % (i+1))}")
  
    zoom_images -= 1
  
    img = img_n.copy if zoom_images == 0 || zoom_changed_small_size <= zoom_small_size
  
    img_n.destroy!
  
  else
  
    img.write("#{sprintf("img_%04d.jpg" % (i+1))}")
  
    puts "Writing - #{img.filename}"
  
  end
  
  end

  Then ffmpeg -y -f image2 -r 30 -i img_%04d.jpg -crf 0 -preset ultrafast -tune stillimage -pix_fmt yuv420p out.mp4

• FFMPEG Video Thumbnail images Php

  20 juillet 2014, par rdxhere

  I need to get middle of video frame depend on video duration.

  I set the $frame = $mov->getFrame(480) ; it’s get only when the 480 frame. I need to set middle of the frame image. Here is code :

      <?php
  
  
  
  $W = intval($_GET['W']);
  
  $H = intval($_GET['H']);
  
   $pic = ''.htmlspecialchars($_GET['file']).''; 
  
  $name = 'wapadmin/'.str_replace('/','--',$pic).'.gif';
  
  $location = 'http://'.str_replace(array('\\','//'),array('/','/'),$_SERVER['HTTP_HOST'].dirname($_SERVER['PHP_SELF']).'/'.$name);
  
  
  
  if(file_exists($name)){
  
  header('Location: '.$location, true, 301);
  
  exit;
  
  }
  
  
  
  $mov = new ffmpeg_movie($pic, false);
  
  $wn = $mov->GetFrameWidth();
  
  $hn = $mov->GetFrameHeight();
  
  
  
  
  
  $frame = $mov->getFrame(480);
  
  
  
  $gd = $frame->toGDImage();
  
  
  
  if(!$W and !$H){
  
  $a = "131*79";
  
  $size = explode('*',$a);
  
  $W = round(intval($size[0])); 
  
  $H = round(intval($size[1])); 
  
  }
  
  
  
  
  
  $new = imageCreateTrueColor($W, $H);
  
  imageCopyResampled($new, $gd, 0, 0, 0, 0, $W, $H, $wn, $hn);
  
  imageGif($new, $name, 100);
  
  
  
  header('Location: '.$location, true, 301);
  
  ?>