code: public float computeRawY(float valueY) {
          final float pixelOffset = (valueY - currentViewport.bottom) * (contentRectMinusAllMargins.height() /
                  currentViewport.height());
          return contentRectMinusAllMargins.bottom - pixelOffset;
      }
docs: Translates chart value into raw pixel value. Returned value is absolute pixel Y coordinate. If this method
  return
  0 that means top most pixel of the screen.