How to split a PDF page in java?

Question

Given a PDF file with a page of any paper size(A0, A1, custom, etc), how can I split the page into different pages, each of the same size say, A4 and save it to a new PDF document in java? I tried using iText library but I had no success.

Answer 1

This task is similar to the task implemented in this answer, the splitting merely is not only in one dimension but in two dimensions.

A possible solution, therefore, can be implemented along the lines of the AbstractPdfPageSplittingTool used there.

So, again we have an abstract splitter class

public abstract class Abstract2DPdfPageSplittingTool {
    public void split(OutputStream outputStream, PdfReader... inputs) throws DocumentException, IOException {
        try {
            initDocument(outputStream);
            for (PdfReader reader : inputs) {
                split(reader);
            }
        } finally {
            closeDocument();
        }
    }

    void initDocument(OutputStream outputStream) throws DocumentException {
        final Document document = new Document(PageSize.A4);
        final PdfWriter writer = PdfWriter.getInstance(document, outputStream);
        this.document = document;
        this.writer = writer;
    }

    void closeDocument() {
        try {
            document.close();
        } finally {
            this.document = null;
            this.writer = null;
        }
    }

    void newPage(Rectangle pageSize) {
        document.setPageSize(pageSize);
        if (!document.isOpen())
            document.open();
        else
            document.newPage();
    }

    void split(PdfReader reader) throws IOException {
        for (int page = 1; page <= reader.getNumberOfPages(); page++) {
            split(reader, page);
        }
    }

    void split(PdfReader reader, int page) throws IOException
    {
        PdfImportedPage importedPage = writer.getImportedPage(reader, page);

        Rectangle pageSizeToImport = reader.getPageSize(page);
        Iterable<Rectangle> rectangles = determineSplitRectangles(reader, page);

        for (Rectangle rectangle : rectangles) {
            newPage(rectangle);
            PdfContentByte directContent = writer.getDirectContent();
            directContent.saveState();
            directContent.rectangle(rectangle.getLeft(), rectangle.getBottom(), rectangle.getWidth(), rectangle.getHeight());
            directContent.clip();
            directContent.newPath();

            writer.getDirectContent().addTemplate(importedPage, -pageSizeToImport.getLeft(), -pageSizeToImport.getBottom());

            directContent.restoreState();
        }
    }

    protected abstract Iterable<Rectangle> determineSplitRectangles(PdfReader reader, int page);

    Document document = null;
    PdfWriter writer = null;
}

(Abstract2DPdfPageSplittingTool.java)

This utility allows to split each source page into a custom set of result pages each of which may represent an arbitrary rectangular (with edges parallel to the corresponding page edges) part of the source page.

You can use the tool like this for splitting pages along a grid of A4 cells:

Abstract2DPdfPageSplittingTool tool = new Abstract2DPdfPageSplittingTool() {
    @Override
    protected Iterable<Rectangle> determineSplitRectangles(PdfReader reader, int page) {
        Rectangle targetSize = PageSize.A4;
        List<Rectangle> rectangles = new ArrayList<>();
        Rectangle pageSize = reader.getPageSize(page);
        for (float y = pageSize.getTop(); y > pageSize.getBottom() + 5; y-=targetSize.getHeight()) {
            for (float x = pageSize.getLeft(); x < pageSize.getRight() - 5; x+=targetSize.getWidth()) {
                rectangles.add(new Rectangle(x, y - targetSize.getHeight(), x + targetSize.getWidth(), y));
            }
        }
        return rectangles;
    }
};
tool.split(RESULT_OUTPUT_STREAM, new PdfReader(SOURCE_PDF));

(based on the SplitPages test testSplitDocumentA6)

Because there is a certain tolerance in the specification of paper sizes, I drop Rectangles which would contain only a very small band from the original document on the left or at the top to prevent empty result pages, assuming that these bands are completely contained in the original page margin. If you don't want that, remove (or change) the + 5 or - 5 in the sample determineSplitRectangles loops.