title: Adding flextable including images in PowerPoint
body: <p>I'm trying to add a flextable object including an image to PowerPoint using officer. But the image disappears. I can reproduce the problem using the example David has posted <a href="https://stackoverflow.com/questions/48580974/adding-image-to-flextable-using-function">hear</a></p>
  
  <pre><code>library(flextable)
  library(tibble)
  download.file("https://www.r-project.org/logo/Rlogo.png", destfile = "Rlogo.png")
  pupil.tbl &lt;- tribble(
      ~col1, ~col2, ~col3,
      "A", "B", "Rlogo.png",
      "C", "D", "Rlogo.png"
  ) 
  pupil.tbl &lt;- as.data.frame(pupil.tbl)
  
  # display only col1 and col2
  pupil.ft &lt;- flextable(pupil.tbl, col_keys = c("col1", "col2") )
  
  add_img_to_flextable &lt;- function(ft, i, j){
  display(
     ft, i=i, col_key = j, pattern = "{{att_tbl}}",
     formatters = list(# use col3 even if not displayed
          att_tbl ~ as_image(col3, src = col3, width = 1.29, height = 1)
     )
  )
  }
  
  pupil.ft &lt;- add_img_to_flextable(pupil.ft, i = 2, j = "col2")
  </code></pre>
  
  <p>If I run:</p>
  
  <pre><code>print(pupil.ft,preview='html')
  print(pupil.ft,preview='docx')
  </code></pre>
  
  <p>everything works fine, but in PPTX format the image isn't shown anymore
      print(pupil.ft,preview='pptx')</p>
  
  <p>Is this a known limitation of PowerPoint? Is there any workaround how to show the images inside a table?</p>
  
  <p>Thanks,</p>
  
  <p>Philipp</p>