code: protected float getXSource(int x, float destLeft, float srcLeft,
  			float widthRatio) {
  
  		float dest = getXEncodedLocation(x, encoding);
  		float source = getSource(dest, destLeft, srcLeft, widthRatio);
  
  		return source;
  	}
docs: Determine the x source pixel location
  
  @param x
  x pixel
  @param destLeft
  destination left most pixel
  @param srcLeft
  source left most pixel
  @param widthRatio
  source over destination width ratio
  @return x source pixel