title: Corona SDK - display.newImageRect is not working
body: <p>I have relatively simple but stupid question, but surprisingly could not find solution :(
  I am new to Corona SDK and trying to display an image. All images are place in directory <code>images</code> directory relative to <code>main.lua</code>.
  Presently i am doing like this</p>
  
  <pre><code>local IMAGE_DIR = "images";
  local bg = display.newImageRect( IMAGE_DIR.. "/bg.png", 570, 360 )
  mainScreenGroup:insert(bg)
  </code></pre>
  
  <p>and it is working perfectly. But according to documentation, here is the syntax</p>
  
  <pre><code>display.newImageRect( [parentGroup,] filename, [baseDirectory] width, height )
  </code></pre>
  
  <p>i have found that instead of concatenate <code>IMAGE_DIR</code>, i can specify <code>[baseDirectory]</code> and instead of manually inserting into group <code>mainScreenGroup</code>, i can specify <code>[parentGroup,]</code> all in one line. But i am not being able to make it work. I have tried following.</p>
  
  <pre><code>local bg = display.newImageRect( [mainScreenGroup,] "bg.png", [IMAGE_DIR] 570, 360 )
  local bg = display.newImageRect( [mainScreenGroup], "bg.png", [IMAGE_DIR], 570, 360 )
  local bg = display.newImageRect( [mainScreenGroup], "/bg.png", [IMAGE_DIR], 570, 360 )
  local bg = display.newImageRect( mainScreenGroup, "/bg.png", IMAGE_DIR, 570, 360 )
  local bg = display.newImageRect( mainScreenGroup, "bg.png", IMAGE_DIR, 570, 360 )
  </code></pre>
  
  <p>But nothing of the above 5 statements working. Am i doing wrong? Any help is appreciated.</p>