Capture Screen with post effect

Hello. I search my problem but i don't find clear answer. I use Edge Detection and try to save result to render texture then save whole data to png file.

   private void CreateScreenShoot()
     {
         if (DataStorageBase.errorExists == true)
         {
             return;
         }
         TakeScreenshot?.Invoke(false);
 
 
         camera.targetTexture = renderTexture;
         camera.Render();
 
         // read pixels will read from the currently active render texture so make our offscreen 
         // render texture active and then read the pixels
         RenderTexture.active = renderTexture;
         screenShot.ReadPixels(rect, 0, 0);
 
         // reset active camera texture and render texture
         camera.targetTexture = null;
         RenderTexture.active = null;
 
       string filename = DataStorageBase.ChosenImage;
         SaveTexture(filename,screenShot, format);
 
         TakeScreenshot?.Invoke(true);
     }
 
   private static void SaveTexture(string filename, Texture2D screenShot, ImageFormat format)
     {
         // pull in our file header/data bytes for the specified image format (has to be done from main thread)
         byte[] fileHeader = null;
         byte[] fileData = null;
         if (format == ImageFormat.RAW)
         {
             fileData = screenShot.GetRawTextureData();
         }
         else if (format == ImageFormat.PNG)
         {
             fileData = screenShot.EncodeToPNG();
         }
         else if (format == ImageFormat.JPG)
         {
             fileData = screenShot.EncodeToJPG();
         }
         else // ppm
         {
             // create a file header for ppm formatted file
             string headerStr = string.Format("P6\n{0} {1}\n255\n", screenShot.width, screenShot.height);
             fileHeader = System.Text.Encoding.ASCII.GetBytes(headerStr);
             fileData = screenShot.GetRawTextureData();
         }
 
         int x =filename.LastIndexOf("\\");
         string name = filename.Substring(x+1);
         filename = Path.Combine(DataStorageBase.MiniatureDirectory, name.Replace("svg", "png"));//DataStorageBase.MiniaturesSavingExtension);
 
         // create new thread to save the image to file (only operation that can be done in background)
         new System.Threading.Thread(() =>
                                     {
                                         // create file and write optional header with image bytes
                                         var f = System.IO.File.Create(filename);
                                         if (fileHeader != null)
                                             f.Write(fileHeader, 0, fileHeader.Length);
                                         f.Write(fileData, 0, fileData.Length);
                                         f.Close();
                                     }).Start();
 
 
     }

But the problem is that i dont know how to transmit image from post process effect to camera target texture. Can anyone solve this problem and give me some advices?