code: protected void interpolateFlowScale(GrayF32 prev, GrayF32 curr) {
  		interp.setImage(prev);
  
  		float scaleX = (float)prev.width/(float)curr.width;
  		float scaleY = (float)prev.height/(float)curr.height;
  
  		float scale = (float)prev.width/(float)curr.width;
  
  		int indexCurr = 0;
  		for( int y = 0; y < curr.height; y++ ) {
  			float yy = y*scaleY;
  			for( int x = 0; x < curr.width; x++ ) {
  				float xx = x*scaleX;
  				if( interp.isInFastBounds(xx,yy)) {
  					curr.data[indexCurr++] = interp.get_fast(x * scaleX, y * scaleY) / scale;
  				} else {
  					curr.data[indexCurr++] = interp.get(x * scaleX, y * scaleY) / scale;
  				}
  			}
  		}
  	}
docs: Takes the flow from the previous lower resolution layer and uses it to initialize the flow
  in the current layer.  Adjusts for change in image scale.