Hello,
i have a problem with highlighting some text pieces in an existing pdf file. I
wanted to create some colored Rectangles in the background of an existing pdf
(portrait layout).
Using the Overlay class, i need to generate a seperate overlay.pdf file, which
can be merged afterwards.
I have used the PDFTextStripper class to extract coordinates of some glyphs
(TextPosition.class).
The problem is, that these coodinates do not match, when i create and write
some rectangles to the overlay.pdf and then try to merge via the Overlay.class .
The rectangles seem to be shifted slightly to the left and the bottom.
I assume, there is some additional coordinate translation required. But i don't
know what translations are used by the PDFTextStripper.
Transformation of the y-coordinate ( lower-left /upper-left coord system)
cannot be sufficient, since the x coordinate is not correct either.
Inspecting a sample glyph from the TextStripper shows there is a textMatrix
containing x,y-scale factors and some x,y-translation. ==> [10, 0 , 0, 0, 10,
0, 0, 289, 796, 1]
Any ideas how to transform the coords that they match the same text piece in
the pdf?
Below is an except of what i was trying:
String pdfin, pdfoverlay, pdfout = "...";
//parse glyphs from PDF using TextStripper ... (Glyph is a wrapper of
TextPosition.class)
List<List<Glyph>> glyphsByPage;
try (PDDocument pddoc = PDDocument.load(pdfin)) {
glyphsByPage = new GlyphStripper(pddoc).stripGlyphsByPage();
}
//generate Overlayfile with Rectangles for glyphs. ...
try (PDDocument pddoc = new PDDocument()) {
for (int pageIndex = 0; pageIndex < glyphsByPage.size();
++pageIndex) {
PDPage page = new PDPage();
pddoc.addPage(page);
try (PDPageContentStream contentstream = new
PDPageContentStream(pddoc, page, true, false)) {
for (Glyph glyph : glyphsByPage.get(pageIndex)) {
TextPosition tpos = glyph.internal();
contentstream.setStrokingColor(Color.RED);
float glyphBottomY = tpos.getTextMatrix().getValue(2,
1) - glyph.getYDirAdj(); //flipping y-coord
contentstream.addRect(tpos.getXDirAdj(), glyphBottomY,
tpos.getWidth(), tpos.getHeight());
contentstream.closeAndStroke();
contentstream.setNonStrokingColor(Color.GRAY);
contentstream.fillRect(tpos.getXDirAdj(), glyphBottomY,
tpos.getWidth(), tpos.getHeight());
contentstream.closeAndStroke();
}
}
}
pddoc.save(pdfoverlay);
}
// Overlay src-PDF with Rectangles-File now. ...
Overlay overlay = new Overlay();
overlay.setInputFile(pdfin);
overlay.setOutputFile(pdfout);
overlay.setAllPagesOverlayFile(pdfoverlay);
overlay.setOverlayPosition(Overlay.Position.BACKGROUND);
overlay.overlay(new HashMap<Integer, String>(), true);
