Using pdfbox - how to get the font from a COSName? - pdfbox

Question

How to get the font from a COSName?
The solution I'm looking for looks somehow like this:
COSDictionary dict = new COSDictionary();
dict.add(fontname, something); // fontname COSName from below code
PDFontFactory.createFont(dict);
If you need more background, I added the whole story below:
I try to replace some string in a pdf. This succeeds (as long as all text is stored in one token). In order to keep the format I like to re-center the text. As far as I understood I can do this by getting the width of the old string and the new one, do some trivial calculation and setting the new position.
I found some inspiration on stackoverflow for replacing https://stackoverflow.com/a/36404377 (yes it has some issues, but works for my simple pdf's. And How to center a text using PDFBox. Unfortunatly this example uses a font constant.
So using the first link's code I get a handling for operator 'TJ' and one for 'Tj'.
PDFStreamParser parser = new PDFStreamParser(page);
parser.parse();
java.util.List<Object> tokens = parser.getTokens();
for (int j = 0; j < tokens.size(); j++)
{
Object next = tokens.get(j);
if (next instanceof Operator)
{
Operator op = (Operator) next;
// Tj and TJ are the two operators that display strings in a PDF
if (op.getName().equals("Tj"))
{
// Tj takes one operator and that is the string to display so lets
// update that operator
COSString previous = (COSString) tokens.get(j - 1);
String string = previous.getString();
String replaced = prh.getReplacement(string);
if (!string.equals(replaced))
{ // if changes are there, replace the content
previous.setValue(replaced.getBytes());
float xpos = getPosX(tokens, j);
//if (true) // center the text
if (6 * xpos > page.getMediaBox().getWidth()) // check if text starts right from 1/xth page width
{
float fontsize = getFontSize(tokens, j);
COSName fontname = getFontName(tokens, j);
// TODO
PDFont font = ?getFont?(fontname);
// TODO
float widthnew = getStringWidth(replaced, font, fontsize);
setPosX(tokens, j, page.getMediaBox().getWidth() / 2F - (widthnew / 2F));
}
replaceCount++;
}
}
Considering the code between the TODO tags, I will get the required values from the token list. (yes this code is awful, but for now it let's me concentrate on the main issue)
Having the string, the size and the font I should be able to call the getWidth(..) method from the sample code.
Unfortunatly I run into trouble to create a font from the COSName variable.
PDFont doesn't provide a method to create a font by name.
PDFontFactory looks fine, but requests a COSDictionary. This is the point I gave up and request help from you.

Answer 1

The names are associated with font objects in the page resources.
Assuming you use PDFBox 2.0.x and that page is a PDPage instance, you can resolve the name fontname using:
PDFont font = page.getResources().getFont(fontname);
But the warning from the comments to the questions you reference remain: This approach will work only for very simple PDFs and might even damage other ones.

Answer 2

try {
//Loading an existing document
File file = new File("UKRSICH_Mo6i-Spikyer_z1560-FAV.pdf");
PDDocument document = PDDocument.load(file);
PDPage page = document.getPage(0);
PDResources pageResources = page.getResources();
System.out.println(pageResources.getFontNames() );
for (COSName key : pageResources.getFontNames())
{
PDFont font = pageResources.getFont(key);
System.out.println("Font: " + font.getName());
}
document.close();
}