'**SUMMARY**
Get the ROI as a list of four points that make up the bounding rectangle.
Each point is represented in unit coordinates with respect to the
souce image.
**RETURNS**
A list of the form [(x,y),(x,y),(x,y),(x,y)]
**EXAMPLE**
>>> roi = ROI(10,10,100,100,img)
>>> print roi.toUnitPoints()'

def toUnitPoints(self):

    if (self.image is None):
        return None
    srcw = float(self.image.width)
    srch = float(self.image.height)
    pts = self.toPoints()
    retVal = []
    for p in pts:
        (x, y) = p
        if (x != 0):
            x = (x / srcw)
        if (y != 0):
            y = (y / srch)
        retVal.append((x, y))
    return retVal
