'**SUMMARY**
show the Pixel Veloctiy (pixels/second) of the object in text on the current frame.
**PARAMETERS**
* *pos* - A tuple consisting of x, y values. where to put to the text
* *color* - The color to draw the object. Either an BGR tuple or a member of the :py:class:`Color` class.
* *size* - Fontsize of the text
**RETURNS**
Nada. Nothing. Zilch.
**EXAMPLE**
>>> while True:
... img1 = cam.getImage()
... ts = img1.track("camshift", ts1, img, bb)
... ts.showPixelVelocityRT() # For continuous bounding box
... img = img1'

def showPixelVelocityRT(self, pos=None, color=Color.GREEN, size=None):

    ts = self
    f = ts[(-1)]
    img = f.image
    vel_rt = f.rt_vel
    if (not pos):
        imgsize = img.size()
        pos = ((imgsize[0] - 120), 90)
    if (not size):
        size = 16
    text = ('Vx    =    %.2f    Vy    =    %.2f' % (vel_rt[0], vel_rt[1]))
    img.drawText(text, pos[0], pos[1], color, size)
    img.drawText('in    pixels/second', pos[0], (pos[1] + size), color, size)
