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    3. GroupDocs.Viewer Product Family
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    5. GroupDocs.Viewer for Node.js
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    7. Document rendering basics
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    9. Render Text documents

    Render text documents as HTML, PDF, and image files

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    GroupDocs.Viewer for Node.js allows you to convert text documents to HTML, PDF, PNG, and JPEG formats so you can view document content in a web browser, PDF or image viewer application.

    To start with the GroupDocs.Viewer API, create a Viewer class instance. Pass a text document you want to view to the class constructor. You can load the document from a file or stream. Call one of the Viewer.view method overloads to convert the image to HTML, PDF, PNG, or JPEG format. These methods allow you to render the entire document or specific pages.

    View text files online View demos and examples on GitHub

    Supported text file formats

    GroupDocs.Viewer supports the following text and programming file formats:

    When you load a text document from a file, you should explicitly specify their format. To do this, create a LoadOptions class instance and use the FileType method. Then pass this instance to the Viewer class constructor.

    // Specify the file encoding. 
const loadOptions = new LoadOptions(FileType.MD)
// Convert the document to PDF.
const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt", loadOptions)
const viewOptions = groupdocs.viewer.PdfViewOptions("output.pdf")
viewer.view(viewOptions)

    Render text files as HTML

    Create an HtmlViewOptions class instance and pass it to the Viewer.view method to convert a text file to HTML. The HtmlViewOptions class properties allow you to control the conversion process. For instance, you can embed all external resources in the generated HTML file, minify the output file, and optimize it for printing. Refer to the following documentation section for details: Rendering to HTML.

    Create HTML files with embedded resources

    To save all elements of an HTML page (including text, graphics, and stylesheets) into a single file, call the HtmlViewOptions.forEmbeddedResources method and specify the output file name.

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Convert the text file to HTML.
// {0} is replaced with the current page number in the output file names.
const viewOptions = groupdocs.viewer.HtmlViewOptions.forEmbeddedResources("page_{0}.html")
viewer.view(viewOptions)

    The following image demonstrates the result:

    Render a text file to HTML

    Create HTML files with external resources

    If you want to store output HTML files and additional resource files (such as fonts, images, and style sheets) separately, call the HtmlViewOptions.forExternalResources method and pass the following parameters:

    • The output file path format
    • The path format for the folder with external resources
    • The resource URL format
    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Create an HTML file for each PDF page.
// Specify the HTML file names and location of external resources.
// {0} and {1} are replaced with the current page number and resource name, respectively.
const viewOptions = groupdocs.viewer.HtmlViewOptions.forExternalResources("page_{0}.html", "page_{0}/resource_{0}_{1}", "page_{0}/resource_{0}_{1}")
viewer.view(viewOptions)

    The image below demonstrates the result. External resources are placed in a separate folder.

    Place HTML resources in a separate folder

    Create a single HTML page

    If you need to display the entire document content on a single HTML page, use the HtmlViewOptions.setRenderToSinglePage method, as shown below:

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Create an HTML file.
const viewOptions = groupdocs.viewer.HtmlViewOptions.forEmbeddedResources("output.html")
// Render the file to a single page. 
viewOptions.setRenderToSinglePage(true)
viewer.view(viewOptions)

    Render text files as PDF

    Create a PdfViewOptions class instance and pass it to the Viewer.view method to convert a text file to PDF. The PdfViewOptions class properties allow you to control the conversion process. For instance, you can protect the output PDF file, reorder its pages, and specify the quality of document images. Refer to the following documentation section for details: Rendering to PDF.

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Convert the text file to PDF.
const viewOptions = groupdocs.viewer.PdfViewOptions("output.pdf")
viewer.view(viewOptions)

    The following image demonstrates the result:

    Render a text file to PDF

    Render text files as PNG

    Create a PngViewOptions class instance and pass it to the Viewer.view method to convert a text file to PNG. Use the PngViewOptions.setHeight and PngViewOptions.setWidth methods to specify the output image size in pixels.

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Convert the text file to PNG.
// {0} is replaced with the current page number in the output image names.
const viewOptions = groupdocs.viewer.PngViewOptions("output_{0}.png")
// Set width and height.
viewOptions.setWidth(950)
viewOptions.setHeight(550)
viewer.view(viewOptions)

    The following image demonstrates the result:

    Render a text file to PNG

    Render text files as JPEG

    Create a JpgViewOptions class instance and pass it to the Viewer.view method to convert a text file to JPEG. Use the JpgViewOptions.setHeight and JpgViewOptions.setWidth methods to specify the output image size in pixels.

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
// Convert the text file to JPEG.
// {0} is replaced with the current page number in the output image names.
const viewOptions = groupdocs.viewer.JpgViewOptions("output_{0}.jpg")
// Set width and height.
viewOptions.setWidth(950)
viewOptions.setHeight(550)
viewer.view(viewOptions)

    Specify rendering options

    GroupDocs.Viewer supports the TextOptions class that allows you to specify different options for rendering text files. To access these options, use the setTextOptions method for one of the following classes (depending on the output file format):

    The TextOptions class supports the following methods:

    • setMaxRowsPerPage—Specifies the maximum number of rows per page. The default value is 55.

    • setMaxCharsPerRow—Specifies the maximum number of characters per row. The default value is 85.

    The following example demonstrates how to change the number of rows displayed on each HTML page:

    const viewer = new groupdocs.viewer.Viewer("TermsOfService.txt")
 // Convert the text file to HTML.
// {0} is replaced with the current page number in the output file names.
const viewOptions = groupdocs.viewer.HtmlViewOptions.forEmbeddedResources("page_{0}.html")
// Set the maximum number of rows per page.
viewOptions.getTextOptions().setMaxRowsPerPage(30)
viewer.view(viewOptions)

    The image below illustrates the result:

    Specify the number of rows per page

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