code: public void setTrackLocation( int x0 , int y0 , int regionWidth , int regionHeight ) {
  		if( imageWidth < regionWidth || imageHeight < regionHeight)
  			throw new IllegalArgumentException("Track region is larger than input image: "+regionWidth+" "+regionHeight);
  
  		regionOut.width = regionWidth;
  		regionOut.height = regionHeight;
  
  		// adjust for padding
  		int w = (int)(regionWidth*(1+padding));
  		int h = (int)(regionHeight*(1+padding));
  		int cx = x0 + regionWidth/2;
  		int cy = y0 + regionHeight/2;
  
  		// save the track location
  		this.regionTrack.width = w;
  		this.regionTrack.height = h;
  		this.regionTrack.x0 = cx-w/2;
  		this.regionTrack.y0 = cy-h/2;
  
  		stepX = (w-1)/(float)(workRegionSize-1);
  		stepY = (h-1)/(float)(workRegionSize-1);
  
  		updateRegionOut();
  	}
docs: Used to change the track's location. If this method is used it is assumed that tracking is active and that
  the appearance of the target has not changed
  @param x0 top-left corner of region
  @param y0 top-left corner of region
  @param regionWidth region's width
  @param regionHeight region's height