Clip an image with PDFBOX - pdfbox

Question

In PDFBOX, I need to render a polygon with a background image or clip an image with my polygon, as in the screenshot example.
I'm trying to understand how PDContentStream.clip() or PDContentStream.shadingfill() works but this is not clear for me.
example : image clipped with polygon in JavaFX

Answer 1

You don't need PDContentStream.shadingfill() for this task.
All you need is to
define the clip path
clip (and stroke to draw a line along the clip area like in your example)
draw the image.
There is just one complication: The implementer of the PDFBox PDContentStream.clip() method apparently considered the option to both clip and stroke (or fill) a path unnecessary and after clipping immediately dropped the path definition:
public void clip() throws IOException
{
if (inTextMode)
{
throw new IllegalStateException("Error: clip is not allowed within a text block.");
}
writeOperator("W");
// end path without filling or stroking
writeOperator("n");
}
Thus, if you indeed want to clip and stroke using the same path definition, you need to bypass the PDFBox clip method.
So, you can proceed like this
PDDocument doc = new PDDocument();
PDImageXObject pdImage = ...;
int w = pdImage.getWidth();
int h = pdImage.getHeight();
PDPage page = new PDPage();
doc.addPage(page);
PDRectangle cropBox = page.getCropBox();
PDPageContentStream contentStream = new PDPageContentStream(doc, page);
contentStream.setStrokingColor(25, 200, 25);
contentStream.setLineWidth(4);
contentStream.moveTo(cropBox.getLowerLeftX(), cropBox.getLowerLeftY() + h/2);
contentStream.lineTo(cropBox.getLowerLeftX() + w/3, cropBox.getLowerLeftY() + 2*h/3);
contentStream.lineTo(cropBox.getLowerLeftX() + w, cropBox.getLowerLeftY() + h/2);
contentStream.lineTo(cropBox.getLowerLeftX() + w/3, cropBox.getLowerLeftY() + h/3);
contentStream.closePath();
//contentStream.clip();
contentStream.appendRawCommands("W ");
contentStream.stroke();
contentStream.drawImage(pdImage, cropBox.getLowerLeftX(), cropBox.getLowerLeftY(), w, h);
contentStream.close();
doc.save(new File(RESULT_FOLDER, "image-clipped.pdf"));
doc.close();
(AddImage test testImageAddClipped)
which with my example image results in