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GroupDocs.Viewer for Java allows you to render your PDF files in HTML, PNG, and JPEG formats. Use this library to implement a simple PDF viewer within your Java application (web or desktop).
Create a Viewer class instance to get started with the GroupDocs.Viewer API. Pass a 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 document to HTML or image format. These methods allow you to render the entire document or specific pages.
GroupDocs.Viewer supports the following PDF and Page Layout file formats:
- Portable Document Format (.PDF)
- Microsoft XML Paper Specification (.XPS)
- Open XML Paper Specification (.OXPS)
- LaTeX Source Document (.TEX)
Create an HtmlViewOptions class instance and pass it to the Viewer.view method to convert a PDF 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.
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("resume.pdf")) {
// 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:
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("resume.pdf")) {
// 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.
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.
By default, PDF and EPUB documents are rendered to HTML with fixed layout to ensure that the output HTML looks the same as a source document. Rendering to fixed layout means that all the HTML elements are absolutely positioned to the container element. And container element has a fixed size so browser window resizing will not have an effect on the position and size of elements in a document.
The following image demonstrates PDF document rendered HTML with fixed layout:
The HtmlviewOptions.getPdfOptions().setImageQuality() methods allows you to specify the quality of images in the output HTML file. You can set this property to one of the following values:
- ImageQuality.LOW — The image resolution is low (96 DPI), and the image size is small. Use this value to increase the conversion performance.
- ImageQuality.MEDIUM — The image resolution is medium (192 DPI), and the image size is larger compared to the low quality images.
- ImageQuality.HIGH — The image resolution is high (300 DPI), and the image size is big. Use of this value may decrease the conversion performance.
The following code snippet shows how to set the medium image quality when rendering a PDF document to HTML:
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create an HTML files.
// {0} is replaced with the current page number in the file name.
HtmlViewOptions viewOptions = HtmlViewOptions.forEmbeddedResources("page_{0}.html");
// Set image quality to medium.
viewOptions.getPdfOptions().setImageQuality(ImageQuality.MEDIUM);
viewer.view(viewOptions);
}
GroupDocs.Viewer supports the HtmlViewOptions.getPdfOptions().setRenderTextAsImage option that allows you to render text as an image when you convert a PDF file to HTML. In this case, the layout of the output HTML file closely mirrors the layout of the source PDF document.
The following code snippet shows how to enable this option in code:
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create an HTML files.
// {0} is replaced with the current page number in the file name.
HtmlViewOptions viewOptions = HtmlViewOptions.forEmbeddedResources("text-as-image_{0}.html");
// Enable rendering text as image.
viewOptions.getPdfOptions().setRenderTextAsImage(true);
viewer.view(viewOptions);
}
The image below illustrates the result. PDF content is exported to HTML as an image, so users cannot select or copy document text.
When you convert a PDF file to HTML, GroupDocs.Viewer creates an HTML document with a single layer (the z-index is not specified for document elements). This helps increase performance and reduce the output file size. If you convert a PDF document with multiple layers and want to improve the position of document elements in the output HTML file, use the HtmlViewOptions.getPdfOptions().setEnableLayeredRendering method to render text and graphics in the HTML file according to their z-order in the source PDF document.
The following code snippet shows how to enable the multi-layer rendering:
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.HtmlViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create an HTML files.
// {0} is replaced with the current page number in the file name.
HtmlViewOptions viewOptions = HtmlViewOptions.forEmbeddedResources("page_{0}.html");
// Enable the multi-layer rendering.
viewOptions.getPdfOptions().setEnableLayeredRendering(true);
viewer.view(viewOptions);
}
Create a PngViewOptions class instance and pass it to the Viewer.view method to convert a PDF 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("resume.pdf")) {
// Create a PNG image for each PDF 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:
Create a JpgViewOptions class instance and pass it to the Viewer.view method to convert a PDF 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("resume.pdf")) {
// Create a JPG image for each PDF 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);
}
When you render PDF documents as images, GroupDocs.Viewer calculates the optimal image size to achieve better rendering quality. If you want the generated images to be the same size as pages in the source PDF document, use the PdfOptions.setRenderOriginalPageSize method of the PngViewOptions or JpgViewOptions class (depending on the output image format).
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PngViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create a PNG image for each PDF page.
// {0} is replaced with the current page number in the image name.
PngViewOptions viewOptions = new PngViewOptions("output_{0}.png");
// Preserve the size of document pages.
viewOptions.getPdfOptions().setRenderOriginalPageSize(true);
viewer.view(viewOptions);
}
To adjust the display of outline fonts when you convert PDF documents to PNG or JPEG, use the PdfOptions.setEnableFontHinting method, as shown below:
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PngViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create a PNG image for each PDF page.
// {0} is replaced with the current page number in the image name.
PngViewOptions viewOptions = new PngViewOptions("output_{0}.png");
// Enable font hinting
viewOptions.getPdfOptions().setEnableFontHinting(true);
viewer.view(viewOptions);
}
Refer to the following article for more information on font hinting: Font hinting.
When you render PDF files in other formats, GroupDocs.Viewer groups individual characters into words to improve rendering performance. If your document contains hieroglyphic or special symbols, you may need to disable character grouping to generate a more precise layout. To do this, use the PdfOptions.setDisableCharsGrouping method, as shown below:
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PngViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create a PNG image for each PDF page.
// {0} is replaced with the current page number in the image name.
PngViewOptions viewOptions = new PngViewOptions("output_{0}.png");
// Disable character grouping.
viewOptions.getPdfOptions().setDisableCharsGrouping(true);
viewer.view(viewOptions);
}
Use the ViewOptions.setRenderComments method for a target view to display textual annotations (such as text comments, sticky notes, text boxes and callouts) in the output HTML, PNG, or JPEG files.
The code example below renders a PDF file with text comments as an image.
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.PngViewOptions;
// ...
try (Viewer viewer = new Viewer("resume.pdf")) {
// Create a PNG image for each PDF page.
// {0} is replaced with the current page number in the image name.
PngViewOptions viewOptions = new PngViewOptions("output_{0}.png");
// Enable rendering comments.
viewOptions.setRenderComments(true);
viewer.view(viewOptions);
}
The following image illustrates the result:
Follow the steps below to obtain information about a PDF file (the number of pages, page size, and printing permissions):
- Create a ViewInfoOptions instance for a specific view.
- Call the Viewer.getViewInfo method, pass the
ViewInfoOptionsinstance to this method as a parameter, and cast the returned object to the PdfViewInfo type. - Use the
PdfViewInfoclass properties to retrieve document-specific information.
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.ViewInfoOptions;
import com.groupdocs.viewer.results.PdfViewInfo;
// ...
ViewInfoOptions viewInfoOptions = ViewInfoOptions.forHtmlView();
PdfViewInfo viewInfo;
try (Viewer viewer = new Viewer("resume.pdf")) {
viewInfo = (PdfViewInfo) viewer.getViewInfo(viewInfoOptions);
}
// Display information about the PDF document.
System.out.println("File type: " + viewInfo.getFileType());
System.out.println("The number of pages: " + viewInfo.getPages().size());
System.out.println("Is printing allowed: " + viewInfo.isPrintingAllowed());
The following image shows a sample console output:
Use the ViewInfoOptions.setExtractText method to enable PDF text extraction. Use the PdfViewInfo.getPages methods to obtain the list of all document pages, and use the (Page.getLines) method to retrieve text for each line.
import com.groupdocs.viewer.Viewer;
import com.groupdocs.viewer.options.ViewInfoOptions;
import com.groupdocs.viewer.results.Line;
import com.groupdocs.viewer.results.Page;
import com.groupdocs.viewer.results.PdfViewInfo;
// ...
try (Viewer viewer = new Viewer("sample.pdf")) {
ViewInfoOptions viewInfoOptions = ViewInfoOptions.forHtmlView();
viewInfoOptions.setExtractText(true);
PdfViewInfo viewInfo = (PdfViewInfo) viewer.getViewInfo(viewInfoOptions);
// Retrieve text from the PDF file.
System.out.println("Extracted document text:");
for (Page page : viewInfo.getPages()) {
for (Line line : page.getLines()) {
System.out.println(line.getValue());
}
}
}
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