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    7. Document rendering basics
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    9. Render EBooks

    Render EBooks as HTML, PDF, and image files

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    GroupDocs.Viewer for .NET 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 .NET 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 EBookd online View demos and examples on GitHub

    Supported EBooks file formats

    GroupDocs.Viewer supports the following EBooks file formats:

    GroupDocs.Viewer can detect the book format automatically based on information in the file header.

    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.

    using GroupDocs.Viewer;
using GroupDocs.Viewer.Options;
// ...

using (var viewer = new Viewer("abook.epub"))
{
    // Create an HTML file for each document page.
    // {0} is replaced with the current page number in the file name.
    var viewOptions = HtmlViewOptions.ForEmbeddedResources("page_{0}.html");
    viewer.View(viewOptions);
}

    Imports GroupDocs.Viewer
Imports GroupDocs.Viewer.Options
' ...

Module Program
    Sub Main(args As String())
        Using viewer = New Viewer("abook.epub")
            ' Create an HTML file for each document page.
            ' {0} is replaced with the current page number in the file name.
            Dim viewOptions = HtmlViewOptions.ForEmbeddedResources("page_{0}.html")
            viewer.View(viewOptions)
        End Using
    End Sub
End Module

    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
    using GroupDocs.Viewer;
using GroupDocs.Viewer.Options;
// ...

using (var viewer = new Viewer("abook.epub"))
{
    // Create an HTML file for each document 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.
    var viewOptions = HtmlViewOptions.ForExternalResources("page_{0}.html", "page_{0}/resource_{0}_{1}", "page_{0}/resource_{0}_{1}");
    viewer.View(viewOptions);
}

    Imports GroupDocs.Viewer
Imports GroupDocs.Viewer.Options
' ...

Module Program
    Sub Main(args As String())
        Using viewer = New Viewer("abook.epub")
            ' Create an HTML file for each document 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.
            Dim viewOptions = HtmlViewOptions.ForExternalResources("page_{0}.html", "page_{0}/resource_{0}_ {1}", "page_{0}/resource_{0}_{1}")
            viewer.View(viewOptions)
        End Using
    End Sub
End Module

    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 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.

    using GroupDocs.Viewer;
using GroupDocs.Viewer.Options;
// ...

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

    Imports GroupDocs.Viewer
Imports GroupDocs.Viewer.Options
' ...

Module Program
    Sub Main(args As String())
        Using viewer = New Viewer("abook.epub")
            ' Create a PDF file for the document.
            ' Specify the PDF file name.
            Dim viewOptions = New PdfViewOptions("output.pdf")
            viewer.View(viewOptions)
        End Using
    End Sub
End Module

    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 to PNG. Use the PngViewOptions.Height and PngViewOptions.Width properties to specify the output image size in pixels.

    using GroupDocs.Viewer;
using GroupDocs.Viewer.Options;
// ...

using (var 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.
    var viewOptions = new PngViewOptions("output_{0}.png");

    // Set width and height.
    viewOptions.Width = 800;
    viewOptions.Height = 900;
    viewer.View(viewOptions);
}

    Imports GroupDocs.Viewer
Imports GroupDocs.Viewer.Options
' ...

Module Program
    Sub Main(args As String())
        Using 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.
            Dim viewOptions = New PngViewOptions("output_{0}.png")

            ' Set width and height.
            viewOptions.Width = 800
            viewOptions.Height = 900
            viewer.View(viewOptions)
        End Using
    End Sub
End Module
    The following image demonstrates the result:

    Render an EBook to PNG

    Render EBooks as JPEG

    Create a JpgViewOptions class instance and pass it to the Viewer.View method to convert an EBook to JPEG. Use the JpgViewOptions.Height and JpgViewOptions.Width properties to specify the output image size in pixels.

    using GroupDocs.Viewer;
using GroupDocs.Viewer.Options;
// ...

using (var viewer = new Viewer("abook.epub"))
{
    // Create a JPEG image for each document page.
    // {0} is replaced with the current page number in the image name.
    var viewOptions = new JpgViewOptions("output_{0}.jpg");
    
    // Set width and height.
    viewOptions.Width = 800;
    viewOptions.Height = 900;
    viewer.View(viewOptions);
}

    Imports GroupDocs.Viewer
Imports GroupDocs.Viewer.Options
' ...

Module Program
    Sub Main(args As String())
        Using viewer = New Viewer("abook.epub")
            ' Create a JPEG image for each document page.
            ' {0} is replaced with the current page number in the image name.
            Dim viewOptions = New JpgViewOptions("output_{0}.jpg")

            ' Set width and height.
            viewOptions.Width = 800
            viewOptions.Height = 900
            viewer.View(viewOptions)
        End Using
    End Sub
End Module

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