Image in front of text - CENTER

I have the following XML

    CTGraphicalObject graphicalobject = drawing.getInlineArray(0).getGraphic();
    long width = drawing.getInlineArray(0).getExtent().getCx();
    long height = drawing.getInlineArray(0).getExtent().getCy();
        String anchorXML = "<wp:anchor xmlns:wp=\"http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing\" "
            +"simplePos=\"0\" relativeHeight=\"0\" behindDoc=\""+((behind)?1:0)+"\" locked=\"0\" layoutInCell=\"1\" allowOverlap=\"1\">"
            +"<wp:simplePos x=\"0\" y=\"0\"/>"
            +"<wp:positionH relativeFrom=\"column\"><wp:posOffset>0</wp:posOffset></wp:positionH>"
            +"<wp:positionV relativeFrom=\"paragraph\"><wp:posOffset>0</wp:posOffset></wp:positionV>"
            +"<wp:extent cx=\""+width+"\" cy=\""+height+"\"/>"
            +"<wp:effectExtent l=\"0\" t=\"0\" r=\"0\" b=\"0\"/><wp:wrapNone/>"
            +"<wp:docPr id=\"1\" name=\"Drawing 0\" descr=\""+drawingDescr+"\"/><wp:cNvGraphicFramePr/>"
            +"</wp:anchor>";

    drawing = CTDrawing.Factory.parse(anchorXML);
    CTAnchor anchor = drawing.getAnchorArray(0);
    anchor.setGraphic(graphicalobject);
    return anchor;  

found here at Wrap Text in Apache POI(docx)?

But for some reason I can't position the image correctly, how do I CENTER it?

How to get usable XML for this?

All Office Open XML files (so also *.docx) simply are ZIP archives. So one can unzip a *.docx file and have a look into. In that ZIP archive you will find a /word/document.xml containing the XML for the document.

So create what you want using Microsoft Word, save the *.docx file, unzip the *.docx file and have a look at what /word/document.xml contains.

In addition, you can use available specifications to read what that XML is supposed to mean. For example learn.microsoft.com and/or ECMA-376 Office Open XML file formats.

For a horizontally centered picture for example, you will find something like :

<wp:anchor … >  
  <wp:positionH relativeFrom="page">  
    <wp:align>center</wp:align>  
  </wp:positionH>  
  …  
</wp:anchor>  

Then try recreating this using code.

Example:

import java.io.*;

import org.apache.poi.xwpf.usermodel.*;

import org.apache.poi.util.Units;

import org.openxmlformats.schemas.wordprocessingml.x2006.main.CTDrawing;
import org.openxmlformats.schemas.drawingml.x2006.main.CTGraphicalObject;
import org.openxmlformats.schemas.drawingml.x2006.wordprocessingDrawing.CTAnchor;

public class CreateWordImageAtCenterOfPage {

 private static CTAnchor getAnchorWithGraphic(CTDrawing drawing /*inline drawing*/ , 
  String drawingDescr, boolean behind, String relFromH, String alignH, String relFromV, String alignV) throws Exception {

  CTGraphicalObject graphicalobject = drawing.getInlineArray(0).getGraphic();
  long width = drawing.getInlineArray(0).getExtent().getCx();
  long height = drawing.getInlineArray(0).getExtent().getCy();

  String anchorXML = 
   "<wp:anchor xmlns:wp=\"http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing\" "
  +"simplePos=\"0\" relativeHeight=\"0\" behindDoc=\""+((behind)?1:0)+"\" locked=\"0\" layoutInCell=\"1\" allowOverlap=\"1\">"
  +"<wp:simplePos x=\"0\" y=\"0\"/>"
  +"<wp:positionH relativeFrom=\""+relFromH+"\"><wp:align>"+alignH+"</wp:align></wp:positionH>"
  +"<wp:positionV relativeFrom=\""+relFromV+"\"><wp:align>"+alignV+"</wp:align></wp:positionV>"
  +"<wp:extent cx=\""+width+"\" cy=\""+height+"\"/>"
  +"<wp:effectExtent l=\"0\" t=\"0\" r=\"0\" b=\"0\"/><wp:wrapNone/>"
  +"<wp:docPr id=\"1\" name=\"Drawing 0\" descr=\""+drawingDescr+"\"/><wp:cNvGraphicFramePr/>"
  +"</wp:anchor>";

  drawing = CTDrawing.Factory.parse(anchorXML);
  CTAnchor anchor = drawing.getAnchorArray(0);
  anchor.setGraphic(graphicalobject);
  return anchor;  
 }

 public static void main(String[] args) throws Exception {

  XWPFDocument doc = new XWPFDocument();
  XWPFParagraph paragraph;
  XWPFRun run; 
  InputStream in;
  CTDrawing drawing;
  CTAnchor anchor;

  paragraph = doc.createParagraph();
  run = paragraph.createRun();
  run.setText("Picture at position center of page:");

  run = paragraph.createRun();
  in = new FileInputStream("samplePict.jpeg");
  int width = Units.toEMU(200);
  int height = Units.toEMU(200);
  run.addPicture(in, Document.PICTURE_TYPE_JPEG, "samplePict.jpeg", width, height);
  in.close();  
  drawing = run.getCTR().getDrawingArray(0);

  anchor = getAnchorWithGraphic(drawing, "samplePict.jpeg", false /*behind text*/, "page", "center", "page", "center");

  drawing.setAnchorArray(new CTAnchor[]{anchor});
  drawing.removeInline(0);

  paragraph = doc.createParagraph();

  FileOutputStream out = new FileOutputStream("./CreateWordImageAtCenterOfPage.docx");
  doc.write(out);
  out.close();
  doc.close();

 }
}