title: R ggplot2: annotation_custom of raster grob does not plot
body: <p><strong><em>UPDATE</em></strong>
  <em>Turns out it was an issue of not being able to produce raster graphics over a remote desktop connection.</em></p>
  
  <p>I want to insert an image from file into a plot made with ggplot2.  This question has already been asked here (<a href="https://stackoverflow.com/questions/9917049/inserting-an-image-to-ggplot2">Inserting an image to ggplot2</a>) but for me the accepted answer produces a plot devoid of any image.  There are no errors or warnings: the axes, grid, and points all plot just fine but there's no R logo (<a href="http://postimg.org/image/rik65wnd7/" rel="nofollow noreferrer">exported plot</a>; I couldn't upload an image here).  Code below:</p>
  
  <pre><code>library(ggplot2)
  library(png)
  library(grid)
  
  img &lt;- readPNG(system.file("img", "Rlogo.png", package="png"))
  g &lt;- rasterGrob(img, interpolate=TRUE)
  
  qplot(1:10, 1:10, geom="blank") +
    annotation_custom(g, xmin=-Inf, xmax=Inf, ymin=-Inf, ymax=Inf) +
    geom_point()
  </code></pre>
  
  <p>I've tried playing around with the xy values and have used several different images and formats but to no avail.</p>
  
  <p>The problem I'm having is specific to using a rastergrob object with annotate_custom(), as the examples given on the <a href="http://docs.ggplot2.org/0.9.3.1/annotation_custom.html" rel="nofollow noreferrer">ggplot2 documentation site for annotate_custom()</a> work just fine, e.g.:</p>
  
  <pre><code>library(gridExtra)
  
  qplot(1:10, 1:10, geom = "blank") + 
    annotation_custom(grob = tableGrob(head(iris[ ,1:3])),
    xmin = 3, xmax = 6, ymin = 2, ymax = 8)
  </code></pre>
  
  <p>I'm using 64-bit R version 3.0.2 on windows with ggplot2 version 0.9.3.1 and my packages are all updated.</p>
  
  <p>Any thoughts would be most welcome, and apologies if I'm missing something simple!</p>