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• Image edited and saved in C# can not be read by ffmpeg

  13 juillet 2017, par mmijic

  I have template image (template.jpg) on which I draw some text (13.07.2017.) and than I save it to another location (temp/intro.jpg).

  Than I want to convert that and some other images into video with ffmpeg.

  If I run command

  ffmpeg.exe -f concat -safe 0 -i input.txt -c:v libx264 -vf "fps=25,format=yuv420p" out.mp4

  Those images gets concentrated into one video file. Problem is that this image edited through C# is black in final video.

  If I for example open that C# created image in Adobe Fireworks and just save it (CTRL+S) without changing anything, and re run ffmpeg command everything is fine.

  This is code which I use to add text to template image

  //INTRO IMAGE CREATION
  
  Bitmap image = new Bitmap(1280, 720);
  
  image.SetResolution(image.HorizontalResolution, image.VerticalResolution);
  
  Graphics g = Graphics.FromImage(image);
  
  g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
  
  g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
  
  g.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
  
  g.TextRenderingHint = TextRenderingHint.AntiAliasGridFit;
  
  StringFormat format = new StringFormat()
  
  {
  
      Alignment = StringAlignment.Near,
  
      LineAlignment = StringAlignment.Near
  
  };
  
  
  
  //template
  
  Bitmap back = new Bitmap(Application.StartupPath + @"\Templates\template.jpg");
  
  g.DrawImage(back, 0, 0, image.Width, image.Height);
  
  
  
  //date
  
  string Date = dateIntro.Value.ToString("dd.MM.yyyy.");
  
  var brush = new SolidBrush(Color.FromArgb(255, 206, 33, 39));
  
  Font font = new Font("Ubuntu", 97, FontStyle.Bold, GraphicsUnit.Pixel);
  
  float x = 617;
  
  float y = 530;
  
  
  
  g.DrawString(Date, font, brush, x, y, format);
  
  g.Flush();
  
  image.Save(Application.StartupPath + @"\temp\intro.jpg", ImageFormat.Jpeg);
  
  image.Dispose();

  Image created this way can be opened and viewed in any program except converted to video with ffmpeg.

  Is there anything I’m missing while adding text and saving image in C# ?

• WriteVideoFrame() with Videocodec.Raw change pixel value

  26 mai 2017, par Alex Gimondi

  I’m using Accord.Video.ffmpeg to record a video in c#. It is actually a depth video with pixels indicating the depth magnitude. From depth array I create a bitmap and the save the bitmap with WriteVideoFrame method.
  Afterward, I open the video in Matlab reading frame by frame. The problem is that I have differences between the bitmap in c# and the frame in Matlab ?! The difference is more or less of 10 (in a range of 255 it’s a big deal)(testing at the moment if it’s constant).
  Since from the bitmap to videoframe I do not perform any operation I think that the problem is in the video encoder. Is is possible even though the format is Raw ?!
  Hints ?
  Alex
  
  UPDATE

  If I run this code in a new project everything is fine

  unsafe private void Button_Click_1(object sender, RoutedEventArgs e)
  
      {
  
          writerdepth.Open("testvideo.avi", 512, 424, 15, VideoCodec.Raw);
  
          for (int i = 0; i code>

  going back to my code when I try to read the image instead of RGB = [100 100 100] I have [96 94 99].
  My starting code is saving depth image from kinect v2, the function is called when a new valid frame arrives.
  I have no idea of the reason for this difference...
  

• matplotlib ArtistAnimation returns a blank video

  28 mars 2017, par Mpaull

  I’m trying to produce an animation of a networkx graph changing over time. I’m using the networkx_draw utilities to create matplotlib figures of the graph, and matplotlib’s ArtistAnimation module to create an animation from the artists networkx produces. I’ve made a minimum reproduction of what I’m doing here :

  import numpy as np
  
  import networkx as nx
  
  import matplotlib.animation as animation
  
  import matplotlib.pyplot as plt
  
  
  
  # Instantiate the graph model
  
  G = nx.Graph()
  
  G.add_edge(1, 2)
  
  
  
  # Keep track of highest node ID
  
  G.maxNode = 2
  
  
  
  fig = plt.figure()
  
  nx.draw(G)
  
  ims = []
  
  
  
  for timeStep in xrange(10):
  
  
  
      G.add_edge(G.maxNode,G.maxNode+1)
  
      G.maxNode += 1
  
  
  
      pos = nx.drawing.spring_layout(G)
  
      nodes = nx.drawing.draw_networkx_nodes(G, pos)
  
      lines = nx.drawing.draw_networkx_edges(G, pos)
  
  
  
      ims.append((nodes,lines,))
  
      plt.pause(.2)
  
      plt.cla()
  
  
  
  im_ani = animation.ArtistAnimation(fig, ims, interval=200,            repeat_delay=3000,blit=True)
  
  im_ani.save('im.mp4', metadata={'artist':'Guido'})

  The process works fine while displaying the figures live, it produces exactly the animation I want. And it even produces a looping animation in a figure at the end of the script, again what I want, which would suggest that the animation process worked. However when I open the "im.mp4" file saved to disk, it is a blank white image which runs for the expected period of time, never showing any of the graph images which were showed live.

  I’m using networkx version 1.11, and matplotlib version 2.0. I’m using ffmpeg for the animation, and am running on a Mac, OSX 10.12.3.

  What am I doing incorrectly ?