How to get a landscape orientation for only some pages while converting html to pdf in itext 7?

Question

I convert HTML to PDF using iText7 with the convertToPDF() method of pdfHTML. I would like to change the page orientation for a few specific pages

Answer 1

Doing it is actually quite tricky, but the whole mechanism is still flexible enough to accommodate this requirement.

We will be working on supporting the following syntax:

<p>Display in portrait</p>
<landscape>
<div>
<p>display in landscape</p>
<p>content</p>
.....
<p>content</p>
</div>
</landscape>
<p> After portrait </p>

First off, we will need to convert the HTML content into elements first and then add those elements into a document instead direct HTML -> PDF conversion. This is needed because in case of HTML there is a separate mechanism for page size handling as dictated by CSS specification and it's not flexible enough to accommodate your requirement so we will be using native iText Layout mechanism for that.

The idea is that apart from customizing the new page size by passing an argument to AreaBreak we will also change the default page size for PdfDocument so that all the consequent pages are created with that custom new page size. For that we will need to pass PdfDocument all along. The high-level code looks as follows:

PdfDocument pdfDocument = new PdfDocument(new PdfWriter(outFilePath));
ConverterProperties properties = new ConverterProperties();
properties.setTagWorkerFactory(new CustomTagWorkerFactory(pdfDocument));

Document document = new Document(pdfDocument);
List<IElement> elements = HtmlConverter.convertToElements(new FileInputStream(inputHtmlPath), properties);
for (IElement element : elements) {
    if (element instanceof IBlockElement) {
        document.add((IBlockElement) element);
    }
}

pdfDocument.close();

The custom tag worker factory is also almost unchanged - it just passes PdfDocument along to the tag worker:

private static class CustomTagWorkerFactory extends DefaultTagWorkerFactory {
    PdfDocument pdfDocument;

    public CustomTagWorkerFactory(PdfDocument pdfDocument) {
        this.pdfDocument = pdfDocument;
    }

    @Override
    public ITagWorker getCustomTagWorker(IElementNode tag, ProcessorContext context) {
        if ("landscape".equalsIgnoreCase(tag.name())) {
            return new LandscapeDivTagWorker(tag, context, pdfDocument);
        }
        return null;
    }
}

The idea of LandscapeDivTagWorker is to create a Div wrapper and put there the inner content of <landscape> tag but also surround it with AreaBreak elements - the preceding one will force the new page break with landscape orientation and change the default page size for the whole document while the succeeding one will revert everything back - force the split to portrait page size and set default page size to portrait as well. Note that we are also setting a custom renderer for AreaBreak with setNextRenderer to actually set the default page size when it comes to that break:

private static class LandscapeDivTagWorker extends DivTagWorker {
    private PdfDocument pdfDocument;

    public LandscapeDivTagWorker(IElementNode element, ProcessorContext context, PdfDocument pdfDocument) {
        super(element, context);
        this.pdfDocument = pdfDocument;
    }

    @Override
    public IPropertyContainer getElementResult() {
        IPropertyContainer baseElementResult = super.getElementResult();
        if (baseElementResult instanceof Div) {
            Div div = new Div();
            AreaBreak landscapeAreaBreak = new AreaBreak(new PageSize(PageSize.A4).rotate());
            landscapeAreaBreak.setNextRenderer(new DefaultPageSizeChangingAreaBreakRenderer(landscapeAreaBreak, pdfDocument));
            div.add(landscapeAreaBreak);
            div.add((IBlockElement) baseElementResult);
            AreaBreak portraitAreaBreak = new AreaBreak(new PageSize(PageSize.A4));
            portraitAreaBreak.setNextRenderer(new DefaultPageSizeChangingAreaBreakRenderer(portraitAreaBreak, pdfDocument));
            div.add(portraitAreaBreak);
            baseElementResult = div;
        }
        return baseElementResult;
    }
}

The implementation of the custom area break renderer is quite straightforward - we only set the default page size to PdfDocument - the rest is done under the hood by default implementations which we extend from:

private static class DefaultPageSizeChangingAreaBreakRenderer extends AreaBreakRenderer {
    private PdfDocument pdfDocument;
    private AreaBreak areaBreak;

    public DefaultPageSizeChangingAreaBreakRenderer(AreaBreak areaBreak, PdfDocument pdfDocument) {
        super(areaBreak);
        this.pdfDocument = pdfDocument;
        this.areaBreak = areaBreak;
    }

    @Override
    public LayoutResult layout(LayoutContext layoutContext) {
        pdfDocument.setDefaultPageSize(areaBreak.getPageSize());
        return super.layout(layoutContext);
    }
}

As a result you will get the page set up similar to the one on the screenshot: