title: Powerpoint change picture without changing cropping area
body: <p>I´ve a cropped picture in a powerpoint layer and I want to change the picture without changing the size of the cropping area. 
  If I change the image by clicking "change picture" the cropping area resizes too, to show the whole picture.
  How can I do that without changing the cropping area? </p>
  
  <p>In Apple Keynote you only have to drag the picture you want to the cropping area and you only have to align it.</p>