private void computeMinimumWidthAndHeight() {
        minViewportWidth = this.maxViewport.width() / maxZoom;
        minViewportHeight = this.maxViewport.height() / maxZoom;
    }
Set maximum zoom level, default is 20.

@param maxZoom
hellocharts-library/src/lecho/lib/hellocharts/computator/ChartComputator.java