PdfBox - 更改矩形中的字体颜色

Question

I'm trying to find certain text in a pdf and making the font color white. As a POC I've already succeeded finding text and highlighting it in the pdf based on the code written by mkl here: find position of text in pdf

Is it however possible, based on the received coordinates to change the font color of the text inside the rectangle instead of highlighting the text? Alternatively, can I add a white rectangle to cover the text?

Thanks in advance

edit: I have started adding the rectangles to the pdf, however as stated they are not in correct position. This is what I have so far (don't mind the style, just a POC):

TextPositionSequence class by mkl

byte[] content = ...;
PDDocument document = PDDocument.load(content);
for (int page = 1; page <= document.getNumberOfPages(); page++) {
            List<TextPositionSequence> hits = null;
            try {
                hits = findSubwordsImproved(document, page, "[" + searchTerm + "]");
            } catch (IOException e) {
                e.printStackTrace();
            }
            for (TextPositionSequence hit : hits) {
                TextPosition lastPosition = hit.textPositionAt(hit.length() - 1);
                TextPosition firstPosition = hit.textPositionAt(0);

                PDPage actualPage = document.getPage(page - 1);

                PDRectangle cropBox = actualPage.getCropBox();

                float x = firstPosition.getTextMatrix().getTranslateX() + cropBox.getLowerLeftX();
                float y = firstPosition.getTextMatrix().getTranslateY() + cropBox.getLowerLeftY();
                float w = hit.getWidth();
                try {
                    PDPageContentStream contents = new PDPageContentStream(document, actualPage, PDPageContentStream.AppendMode.APPEND, false);
                    contents.setNonStrokingColor(Color.RED);
                    contents.addRect(x, y, w, firstPosition.getHeight());
                    contents.fill();
                    contents.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
           }
}

Answer 1

I've solved it with the following code. I fiddled with the rectangle height a bit to get the box to cover the entire text. This might need tweaking in the future:

float posXInit = hit.getX();
float posXEnd = lastPosition.getXDirAdj() + lastPosition.getWidth();
float posYInit = firstPosition.getPageHeight() - firstPosition.getYDirAdj();
float posYEnd = firstPosition.getPageHeight() - lastPosition.getYDirAdj();
float height = firstPosition.getHeight();

PDPageContentStream contents = new PDPageContentStream(document, actualPage, PDPageContentStream.AppendMode.APPEND, false, true);
contents.setNonStrokingColor(Color.WHITE);
contents.addRect(posXInit, posYEnd - height / 3, hit.getWidth(), height * 2);
contents.fill();
contents.close();