Specifies a lower resolution image to display.
Setting the src attribute in code has the side-effect of actually starting to
load the new URL into the image area (and aborting the transfer of any image
data that is already loading into the same area). Therefore, if you're going to
alter the lowsrc property, you need to do so before setting the src property. If
the URL in the src property references an image that is not the same size as the
image cell it is loaded into, the source image is scaled to fit.