我使用以下代码在我的WPF应用程序中使用iTextSharp XMLWorker解析HTML字符串：

var css = "";
using (var htmlMS = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(html)))
{                    
    //Create a stream to read our CSS
    using (var cssMS = new MemoryStream(System.Text.Encoding.UTF8.GetBytes(css)))
    {                        
        //Get an instance of the generic XMLWorker
        var xmlWorker = XMLWorkerHelper.GetInstance();

        //Parse our HTML using everything setup above
        xmlWorker.ParseXHtml(writer, doc, htmlMS, cssMS, System.Text.Encoding.UTF8, fontProv);                        
    }
}

解析工作正常,但它真的很慢,解析HTML大约需要2秒.因此,对于50页的pdf,大约需要2分钟.我在我的HTML字符串中使用内联样式.这是自然行为还是可以优化？

解决方法:

这个问题是错误的,因为它表明HTML解析正在减慢一切.这不是真的.甚至在解析第一个HTML片段之前就会发生瓶颈.

您正在使用最基本的一些代码行来从HTML创建PDF,如ParseHtml示例中所示：

public void createPdf(String file) throws IOException, DocumentException {
    // step 1
    Document document = new Document();
    // step 2
    PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(file));
    // step 3
    document.open();
    // step 4
    XMLWorkerHelper.getInstance().parseXHtml(writer, document,
            new FileInputStream(HTML));
    // step 5
    document.close();
}

这段代码很简单,但它在内部执行了很多操作,如另一个问题的注释所述：XMLWorkerHelper performance slow.

注册字体目录的行为会占用大量时间.您可以通过使用自己的FontProvider来避免这种情况,如ParseHtmlFonts示例中所述.

public void createPdf(String file) throws IOException, DocumentException {
    // step 1
    Document document = new Document();

    // step 2
    PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(file));
    writer.setInitialLeading(12.5f);

    // step 3
    document.open();

    // step 4

    // CSS
    CSSResolver cssResolver = new StyleAttrCSSResolver();
    CssFile cssFile = XMLWorkerHelper.getCSS(new FileInputStream(CSS));
    cssResolver.addCss(cssFile);

    // HTML
    XMLWorkerFontProvider fontProvider = new XMLWorkerFontProvider(XMLWorkerFontProvider.DONTLOOKFORFONTS);
    fontProvider.register("resources/fonts/Cardo-Regular.ttf");
    fontProvider.register("resources/fonts/Cardo-Bold.ttf");
    fontProvider.register("resources/fonts/Cardo-Italic.ttf");
    fontProvider.addFontSubstitute("lowagie", "cardo");
    CssAppliers cssAppliers = new CssAppliersImpl(fontProvider);
    HtmlPipelineContext htmlContext = new HtmlPipelineContext(cssAppliers);
    htmlContext.setTagFactory(Tags.getHtmlTagProcessorFactory());

    // Pipelines
    PdfWriterPipeline pdf = new PdfWriterPipeline(document, writer);
    HtmlPipeline html = new HtmlPipeline(htmlContext, pdf);
    CssResolverPipeline css = new CssResolverPipeline(cssResolver, html);

    // XML Worker
    XMLWorker worker = new XMLWorker(css, true);
    XMLParser p = new XMLParser(worker);
    p.parse(new FileInputStream(HTML));

    // step 5
    document.close();
}

在这种情况下,我们会指导iText DONTLOOKFORFONTS,从而节省大量时间.我们告诉iText我们将在HTML中使用哪些字体,而不是让iText查找字体.