Render EBooks as HTML, PDF, and image files

GroupDocs.Viewer for Java allows you to render your EBooks (EPUB, MOBI) in HTML, PDF, PNG, and JPEG formats. You do not need to use any book reader to load and view EBooks within your Java application (web or desktop).

To start using the GroupDocs.Viewer API, create a Viewer class instance. Pass a book you want to view to the class constructor. You can load the book from a file or stream. Call one of the Viewer.view method overloads to convert the EBook to HTML, PDF, or image format.

View EBooks online View demos and examples on GitHub

Supported EBooks file formats

GroupDocs.Viewer supports the following EBooks file formats:

Render EBooks as HTML

Create an HtmlViewOptions class instance and pass it to the Viewer.view method to convert an EBook 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 an HTML file 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.

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...

try (Viewer viewer = new Viewer("abook.epub")) {
    // Create an HTML files.
    // {0} is replaced with the current page number in the file name.
    HtmlViewOptions viewOptions = HtmlViewOptions.forEmbeddedResources("page_{0}.html");
    viewer.view(viewOptions);
}

The following image demonstrates the result:

Render an EBook to HTML

Create an HTML file with external resources

If you want to store an HTML file and additional resource files (such as fonts, images, and stylesheets) 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
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...

try (Viewer viewer = new Viewer("abook.epub")) {
   // Create an HTML file for each 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.
   HtmlViewOptions viewOptions = 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

Render EBooks as PDF

Create a PdfViewOptions class instance and pass it to the Viewer.view method to convert an EBook 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.

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PdfViewOptions;
// ...

try (Viewer viewer = new Viewer("abook.epub")) {
    // Create a PDF file for the document.
    // Specify the PDF file name.
    PdfViewOptions viewOptions = new PdfViewOptions("output.pdf");
    viewer.view(viewOptions);
}

The following image demonstrates the result:

Render an EBook to PDF

Render EBooks as PNG

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

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PngViewOptions;
// ...

try (Viewer viewer = new Viewer("abook.epub")) {
    // Create a PNG image for each document page.
    // {0} is replaced with the current page number in the image name.
    PngViewOptions viewOptions = new PngViewOptions("output_{0}.png");
    // Set width and height.
    viewOptions.setWidth(950);
    viewOptions.setHeight(550);
    viewer.view(viewOptions);
}
The following image demonstrates the result:

Render an EBook file to PNG

Render EBooks as JPEG

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

import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.JpgViewOptions;
// ...

try (Viewer viewer = new Viewer("abook.epub")) {
    // Create a JPG image for each document page.
    // {0} is replaced with the current page number in the image name.
    JpgViewOptions viewOptions = new JpgViewOptions("output_{0}.jpg");
    // Set width and height.
    viewOptions.setWidth(950);
    viewOptions.setHeight(550);
    viewer.view(viewOptions);
}