How can one programmatically read the graph values from a Powerpoint presentation using Apache's POI?

apache-poi, java, powerpoint

Solution

In the first part we need to navigate to an `XSLFChart` object:

final String filename = "resources/fptbenchmark/Powerpoint Import.pptx";
final XMLSlideShow ppt = new XMLSlideShow(new FileInputStream(filename));

final XSLFSlide slide = ppt.getSlides()[5];

The slide contains different parts (`getRelations()`) one of which should contain the `XSLFChart`:

final List<POIXMLDocumentPart> relations = slide.getRelations();
assert relations.size() == 3;

final XSLFChart xslfChart = (XSLFChart)relations.get(2);

When you examine the `xslfChart` variable in the debugger you will notice that the field `CTChartImpl chart` shows the underlying XML data, which might look like this:

<xml-fragment xmlns:c="http://schemas.openxmlformats.org/drawingml/2006/chart"
xmlns:a="http://schemas.openxmlformats.org/drawingml/2006/main"
xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">
<c:autoTitleDeleted val="0"/>
<c:plotArea>
  <c:scatterChart>
    <c:ser>
      <c:tx>
        <c:strRef>
          <c:f>Sheet1!$E$8</c:f>
          <c:strCache>
            <c:ptCount val="1"/>
            <c:pt idx="0">
              <c:v>y axis caption</c:v>
            </c:pt>
          </c:strCache>
        </c:strRef>
      </c:tx>
      <c:xVal>
        <c:numRef>
          <c:f>Sheet1!$A$9:$A$28</c:f>
          <c:numCache>
            <c:formatCode>General</c:formatCode>
            <c:ptCount val="20"/>
            <c:pt idx="0">
              <c:v>1200</c:v>
            </c:pt>
            <c:pt idx="1">
              <c:v>1600</c:v>
            </c:pt>
            <c:pt idx="2">
              <c:v>2000</c:v>
            </c:pt>
...

You can naviage this tree starting with the `CTChart`:

CTChart ctChart = xslfChart.getCTChart();

Since there is a `<c:plotArea>` tag, you call the associated member function to access it:

CTPlotArea plotArea = ctChart.getPlotArea();

From there you should be able to navigate your way around

List<CTNumVal> ptList = plotArea.getScatterChartList().get(1)
    .getSerList().get(0)
    .getXVal()
    .getNumRef()
    .getNumCache()
    .getPtList();

Now you have access to the values:

ptList.get(0).getV();

References

- ooxml-schemas-1.1.jar

- Ecma-376

Problem

Original source