Apache POI Excel: How to set color transparency in charts? - apache-poi

Question

I'm struggling to solve how to set opacity/transparency/alpha of colors in charts using Apache POI. Using the XDDF classes, there seems to be no way to do this. The Documentation of XDDFColor has no way to set this value when creating this object. The only thing that I thought may have worked was accessing the underlying CTHslColor from the XDDFColor as follows.
XDDFColor xddfColor = XDDFColor.from(PresetColor.LIGHT_GREEN);
CTColor container = xddfColor.getColorContainer();
CTHslColor hslColor = container.addNewHslClr();
CTPositiveFixedPercentage p = hslColor.addNewAlpha();
p.setVal(50000);
XDDFChartData.Series series = data.getSeries(2);
XDDFSolidFillProperties fill = new XDDFSolidFillProperties(xddfColor);
XDDFLineProperties line = new XDDFLineProperties();
line.setFillProperties(fill);
XDDFShapeProperties properties = series.getShapeProperties();
if (properties == null) {
properties = new XDDFShapeProperties();
}
properties.setLineProperties(line);
series.setShapeProperties(properties);
series.setFillProperties(fill);
While the color is correctly set in the chart, the transparency does not work. Is there any way to be able to set the fill color transparency for an Area Chart using POI?

Answer 1

The constructor XDDFSolidFillProperties(XDDFColor) creates a CTSolidColorFillProperties having a CTPresetColor corresponding to the given XDDFColor if that XDDFColor is instanceof XDDFColorPreset. And after that you should set the alpha, instead of manipulating the XDDFColor before. Also you should set fill properties as well as line properties to the XDDFShapeProperties and those to the series then. So:
private static void solidFillSeries(XDDFChartData data, int index, PresetColor color, int alpha) {
XDDFSolidFillProperties fill = new XDDFSolidFillProperties(XDDFColor.from(color));
org.openxmlformats.schemas.drawingml.x2006.main.CTSolidColorFillProperties ctSolidColorFillProperties =
(org.openxmlformats.schemas.drawingml.x2006.main.CTSolidColorFillProperties)fill.getXmlObject();
org.openxmlformats.schemas.drawingml.x2006.main.CTPresetColor ctPresetColor = ctSolidColorFillProperties.getPrstClr();
org.openxmlformats.schemas.drawingml.x2006.main.CTPositiveFixedPercentage ctPositiveFixedPercentage = ctPresetColor.addNewAlpha();
ctPositiveFixedPercentage.setVal(alpha);
XDDFChartData.Series series = data.getSeries(index);
XDDFShapeProperties properties = series.getShapeProperties();
if (properties == null) {
properties = new XDDFShapeProperties();
}
properties.setFillProperties(fill);
XDDFLineProperties line = new XDDFLineProperties();
line.setFillProperties(fill);
properties.setLineProperties(line);
series.setShapeProperties(properties);
}
Complete example:
import java.io.FileOutputStream;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.xddf.usermodel.*;
import org.apache.poi.xddf.usermodel.chart.*;
import org.apache.poi.xssf.usermodel.XSSFClientAnchor;
import org.apache.poi.xssf.usermodel.XSSFDrawing;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
public class CreateExcelXDDFAreaChart {
public static void main(String[] args) throws Exception {
try (XSSFWorkbook document = new XSSFWorkbook()) {
XSSFSheet sheet = document.createSheet("SurfaceChart");
// create the data
String[] categories = new String[] { "c1", "c2", "c3", "c4", "c5", "c6", "c7", "c8", "c9" };
Double[] values1 = new Double[] { 10d, 20d, 10d, 15d, 12d, 20d, 10d, 18d, 19d };
Double[] values2 = new Double[] { 20d, 10d, 15d, 20d, 11d, 17d, 18d, 20d, 10d };
Double[] values3 = new Double[] { 14.5d, 14d, 13.5d, 13d, 12.5d, 12d, 11.5d, 11d, 10.5d };
int r = 0;
for (String cat : categories) {
sheet.createRow(r).createCell(0).setCellValue(cat);
sheet.getRow(r).createCell(1).setCellValue(values1[r]);
sheet.getRow(r).createCell(2).setCellValue(values2[r]);
sheet.getRow(r).createCell(3).setCellValue(values3[r]);
r++;
}
// create the chart
XSSFDrawing drawing = sheet.createDrawingPatriarch();
XSSFClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 5, 0, 20, 30);
XDDFChart chart = drawing.createChart(anchor);
// create data sources
int numOfPoints = categories.length;
XDDFDataSource<String> categoriesData = XDDFDataSourcesFactory.fromStringCellRange(sheet, new CellRangeAddress(0, numOfPoints-1, 0, 0));
XDDFNumericalDataSource<Double> valuesData1 = XDDFDataSourcesFactory.fromNumericCellRange(sheet, new CellRangeAddress(0, numOfPoints-1, 1, 1));
XDDFNumericalDataSource<Double> valuesData2 = XDDFDataSourcesFactory.fromNumericCellRange(sheet, new CellRangeAddress(0, numOfPoints-1, 2, 2));
XDDFNumericalDataSource<Double> valuesData3 = XDDFDataSourcesFactory.fromNumericCellRange(sheet, new CellRangeAddress(0, numOfPoints-1, 3, 3));
// area chart
XDDFCategoryAxis categoryAxis = chart.createCategoryAxis(AxisPosition.BOTTOM);
XDDFValueAxis valueAxis = chart.createValueAxis(AxisPosition.LEFT);
valueAxis.setCrosses(AxisCrosses.AUTO_ZERO);
XDDFChartData data = chart.createData(ChartTypes.AREA, categoryAxis, valueAxis);
XDDFChartData.Series series = data.addSeries(categoriesData, valuesData1);
series.setTitle("Series 1", null);
series = data.addSeries(categoriesData, valuesData2);
series.setTitle("Series 2", null);
series = data.addSeries(categoriesData, valuesData3);
series.setTitle("Series 3", null);
chart.plot(data);
// set legend
XDDFChartLegend legend = chart.getOrAddLegend();
legend.setPosition(LegendPosition.BOTTOM);
solidFillSeries(data, 0, PresetColor.RED, 50000);
solidFillSeries(data, 1, PresetColor.GREEN, 50000);
solidFillSeries(data, 2, PresetColor.BLUE, 50000);
// Write the output to a file
try (FileOutputStream fileOut = new FileOutputStream("./CreateExcelXDDFAreaChart.xlsx")) {
document.write(fileOut);
}
}
}
private static void solidFillSeries(XDDFChartData data, int index, PresetColor color, int alpha) {
XDDFSolidFillProperties fill = new XDDFSolidFillProperties(XDDFColor.from(color));
org.openxmlformats.schemas.drawingml.x2006.main.CTSolidColorFillProperties ctSolidColorFillProperties =
(org.openxmlformats.schemas.drawingml.x2006.main.CTSolidColorFillProperties)fill.getXmlObject();
org.openxmlformats.schemas.drawingml.x2006.main.CTPresetColor ctPresetColor = ctSolidColorFillProperties.getPrstClr();
org.openxmlformats.schemas.drawingml.x2006.main.CTPositiveFixedPercentage ctPositiveFixedPercentage = ctPresetColor.addNewAlpha();
ctPositiveFixedPercentage.setVal(alpha);
XDDFChartData.Series series = data.getSeries(index);
XDDFShapeProperties properties = series.getShapeProperties();
if (properties == null) {
properties = new XDDFShapeProperties();
}
properties.setFillProperties(fill);
XDDFLineProperties line = new XDDFLineProperties();
line.setFillProperties(fill);
properties.setLineProperties(line);
series.setShapeProperties(properties);
}
}
Hint: The value of the CTPositiveFixedPercentagealpha is percentage in units of 1000th (thousandth) percent. So it is from 0 to 100000 and 50000 is 50%.