xlsgen::IXlsChartPtr chart001s0 = worksheet->NewChart(xlsgen::charttype_bar2D, 4, 5, 18, 10);

    xlsgen::IXlsChartDynamicDataSourcePtr datasource001s0 = chart001s0->DynamicDataSource;

    xlsgen::IXlsChartDynamicDataSourceSeriesPtr serie001s0ss0 = datasource001s0->AddSerie();
    serie001s0ss0->SeriesTitlesFormula = L"Sheet1!$C$2";
    serie001s0ss0->SeriesValuesFormula = L"Sheet1!$C$3:$C$10";
    xlsgen::IXlsChartDynamicDataSourceSeriesPtr serie001s0ss1 = datasource001s0->AddSerie();
    serie001s0ss1->SeriesTitlesFormula = L"Sheet1!$D$2";
    serie001s0ss1->SeriesValuesFormula = L"Sheet1!$D$3:$D$10";
    chart001s0->Legend->Show = xlsgen::chartlegend_hidden;

    chart001s0->MainTitle->Label = L"Chart transparency";

    // bar formatting (auto gradient fill, and 94% means we want the 2nd gradient stop almost fully transparent)
    chart001s0->SeriesByIndex[1]->Options->Patterns->Area->FillTransparency[1] = 94;

    // area formatting (50% means we want the solid area half opaque half transparent)
    chart001s0->SeriesByIndex[2]->SeriesType = xlsgen::charttype_area2D;
    chart001s0->SeriesByIndex[2]->Options->Patterns->Area->Type = xlsgen::chartareatype_custom;
    chart001s0->SeriesByIndex[2]->Options->Patterns->Area->Pattern->PatternStyle = xlsgen::chartareapattern_solid;
    chart001s0->SeriesByIndex[2]->Options->Patterns->Area->Pattern->BackgroundColor = 0xFF0000;
    chart001s0->SeriesByIndex[2]->Options->Patterns->Area->FillTransparency[0] = 50;