How to reuse font from one pdf in another in iText7?

Question

I'm trying to open PDF file in iText7, write there some new piece of text, apply font from original PDF to it and save it in another PDF document. I'm using Java 1.8

Thus, I need a set of font names used in original pdf, from where user will choose one, that will be applied to a new paragraph. And I also need to somehow apply this font.

For now I have this piece of code, that I've taken from here:

public static void main(String[] args) throws IOException {
        PdfDocument pdf = new PdfDocument(new PdfReader("example.pdf"));
        Set<PdfName> fonts = listAllUsedFonts(pdf);
        fonts.stream().forEach(System.out::println);
}

public static Set<PdfName> listAllUsedFonts(PdfDocument pdfDoc) throws IOException {
        PdfDictionary acroForm = pdfDoc.getCatalog().getPdfObject().getAsDictionary(PdfName.AcroForm);
        if (acroForm == null) {
            return null;
        }
        PdfDictionary dr = acroForm.getAsDictionary(PdfName.DR);
        if (dr == null) {
            return null;
        }
        PdfDictionary font = dr.getAsDictionary(PdfName.Font);
        if (font == null) {
            return null;
        }
        return font.keySet();
    }

It returns this output:

/Helv
/ZaDb

However, the only font example.pdf has is Verdana (it is what document properties in Adobe Acrobat Pro says). Moreover, there are Verdana in two implementations: Bold and normal.

So, I have these questions:

1. Why does this function returns two fonts instead of one (Verdana).
2. How can I generate normal well-read names of fonts to display them to user (e.g. Helvetica instead of Helv)?
3. How can I apply font got from the original document to the new paragraph?

Thank you in advance!

Answer 1

If you only wish to display the names of the fonts being used (which you are legally allowed to do) you can use the following code:

public void go() throws IOException {

    final Set<String> usedFontNames = new HashSet<>();
    IEventListener fontNameExtractionStrategy = new IEventListener() {
        @Override
        public void eventOccurred(IEventData iEventData, EventType eventType) {
            if(iEventData instanceof TextRenderInfo)
            {
                TextRenderInfo tri = (TextRenderInfo) iEventData;
                String fontName = tri.getFont().getFontProgram().getFontNames().getFontName();
                usedFontNames.add(fontName);
            }
        }
        @Override
        public Set<EventType> getSupportedEvents() {
            return null;
        }
    };

    PdfCanvasProcessor parser = new PdfCanvasProcessor(fontNameExtractionStrategy);

    File inputFile = new File("YOUR_INPUT_FILE_HERE.pdf");
    PdfDocument pdfDocument = new PdfDocument(new PdfReader(inputFile));
    for(int i=1;i<=pdfDocument.getNumberOfPages();i++)
    {
        parser.processPageContent(pdfDocument.getPage(i));
    }
    pdfDocument.close();

    for(String fontName : usedFontNames)
    {
        System.out.println(fontName);
    }
}

Answer 2

You should not reuse a font from one PDF in another PDF, and here's why: fonts are hardly ever fully embedded in a PDF document. For instance: you use the font Verdana regular (238 KB) and the font Verdana bold (207 KB), but when you create a simple PDF document saying "Hello World" in regular and bold, the file size will be much smaller than 238 + 207 KB. Why is this? Because the PDF will only consist of a subset of the font Verdana regular and a subset of the font Verdana bold.

You may have noticed that I am talking of the font Verdana regular and the font Verdana bold. Those are two different fonts from the same font family. Reading your question, I notice that you don't make that distinction. You talk about the font Verdana with two implementations bold and normal. This is incorrect. You should talk about the font family Verdana and two fonts Verdana bold and Verdana regular.

A PDF usually contains subsets of different fonts. It can even contain two different subsets of the same font. See also What are the extra characters in the font name of my PDF?

Your goal is to take the font of one PDF and to use that font of another PDF. However, suppose that your original PDF only contains the subset that is required to write "Hello World" and that you want to create a new PDF saying "Hello Universe." That will never work, because the subset won't contain the glyphs to render the letter U, n, i, v, r, and s.

Also take into account that fonts are usually licensed. Many fonts have a license that states that you can use to font to create a document and embed that font in that document. However, there is often a clause that says that other people are not allowed to extract to font to use it in a different context. For instance: you paid for the font when you purchased a copy of MS Windows, but someone who receives a PDF containing that font may not have a license to use that font. See Does one need to have a license for fonts if we are using ttf files in itext?

Given the technical and legal issues related to your question, I don't think it makes sense to work on a code sample. Your design is flawed. You should work with a licensed font program instead of trying to extract a font from an existing PDF. This answers question 3: How can I apply font got from the original document to the new paragraph? You can't: it is forbidden by law (see Extra info below) and it might be technically impossible if the subset doesn't contain all the characters you need!

Furthermore, the sample you found on the official iText web site looks for the fonts defined in a form. /Helv and ZaDb refer to Helvetica and Zapfdingbats. Those are two fonts of a set of 14 known as the Standard Type 1 fonts. These fonts are never embedded in the document since every viewer is supposed to know how to render them. You don't need a full font program if you want to use these fonts; the font metrics are sufficient. For instance: iText ships with 14 AFM files (AFM = Adobe Font Metrics) that contain the font metrics.

You wonder why you don't find Verdana, since Verdana is used as font for the text in your document, but you are looking at the wrong place. You are asking iText for the fonts used for the form, not for the fonts used in the text. This answer question 1: Why does this function returns two fonts instead of one (Verdana).

As for your question 2: you are looking at the internal name of the font, and that internal name can be anything (even /F1, /F2,...). The postscript name of the font is stored in the font dictionary. That's the name you need.

Extra info:

I checked the Verdana license:

Microsoft supplied font. You may use this font to create, display, and print content as permitted by the license terms or terms of use, of the Microsoft product, service, or content in which this font was included. You may only (i) embed this font in content as permitted by the embedding restrictions included in this font; and (ii) temporarily download this font to a printer or other output device to help print content. Any other use is prohibited.

The use you want to make of the font is prohibited. If you have a license for Verdana, you can embed the font in a PDF. However, it is not permitted to extract that font and use it for another purpose. You need to use the original font program.