Images that are inserted into richedit controls store a space for the
text, since that is the character returned when getting the plain text
from the control.

When calculating the width of a line, the space character is skipped,
but images should not be skipped.  This can be seen by inserting an
image into wordpad on a line by it's own, then centering the line.  The
image will start from the center rather than being centered in the
control.