@Override
    public void onChartSizeChanged() {
        calculateCircleOval();

        if (computator.getChartWidth() > 0 && computator.getChartHeight() > 0) {
            softwareBitmap = Bitmap.createBitmap(computator.getChartWidth(), computator.getChartHeight(),
                    Bitmap.Config.ARGB_8888);
            softwareCanvas.setBitmap(softwareBitmap);
        }
    }
Default renderer for PieChart. PieChart doesn't use viewport concept so it a little different than others chart
types.
hellocharts-library/src/lecho/lib/hellocharts/renderer/PieChartRenderer.java