title: 'rsInvalidImageReference' Warning When Previewing a SSRS Report
body: <p>In an SSRS report:</p>
  
  <p>I am specifying the footer's background image using an expression, so that the image on the first page is different from other pages. </p>
  
  <p>The images are stored as part of the project, and are displaying correctly, however I get this warning</p>
  
  <pre><code>Build complete -- 0 errors, 0 warnings
  
  [rsInvalidImageReference] The Value for the page ‘footer’ is invalid. 
  
  Details: Invalid URI: The format of the URI could not be determined.
  
  Preview complete -- 0 errors, 1 warnings
  </code></pre>
  
  <p>Anyone know what causes this warning, and how I should get rid of it? </p>
  
  <p><strong>Edit: Is it possible to do this, and to avoid using an absolute path?</strong> I need to use relative paths within the project as I cant control where this is getting rolled out to.</p>
  
  <hr>
  
  <p>The expression I'm using to select the image for the Footer/BackgroundImage/Value property is:</p>
  
  <pre><code>= IIf(Globals!PageNumber.Equals(1), "image1.png", "image2.png")
  </code></pre>
  
  <p>Also, I've tried setting the BackgroundImage Source and MIMEType as well to external and image/png, it doesn't seem to make a difference.</p>