Generate previews

GroupDocs.Parser provides the functionality to generate document page previews by generatePreview(PreviewOptions) method:

void generatePreview(PreviewOptions previewOptions)

PreviewOptions class is used to set requirements and stream delegates for preview generation.

Here are the steps to generate document page previews:

The following example shows how to generate document page previews:

// Create an instance of Parser class to generate document page previews
try (Parser parser = new Parser(Constants.SamplePdfWithToc)) {
    // Create preview options
    PreviewOptions previewOptions = new PreviewOptions(
            new ICreatePageStream() {
                @Override
                public OutputStream createPageStream(int pageNumber) {
                    try {
                        return new FileOutputStream(getOutputPath(String.format("preview_%d.png", pageNumber)));
                    } catch (IOException ex) {
                        throw new RuntimeException(ex.getMessage());
                    }
                }
            });
    // Set PNG as an output image format
    previewOptions.setPreviewFormat(PreviewFormats.Png);
    // Set DPI for the output image
    previewOptions.setDpi(72);
    // Generate previews
    parser.generatePreview(previewOptions);
}

private static String getOutputPath(String fileName) throws java.io.IOException {
    return Constants.getOutputFilePath(fileName);
}

Here are the steps to generate spreadsheets page previews:

The following example shows how to generate spreadsheet page previews:

// Create an instance of Parser class to generate spreadsheet page previews
try (Parser parser = new Parser(Constants.SampleXlsx)) {
    final PageRenderInfo[] renderInfo = {null};
    // Create preview options
    PreviewOptions previewOptions = new PreviewOptions(
            new ICreatePageStream() {
                @Override
                public OutputStream createPageStream(int pageNumber) {
                    try {
                        return new FileOutputStream(getOutputPath(renderInfo[0], pageNumber));
                    } catch (IOException ex) {
                        throw new RuntimeException(ex.getMessage());
                    }
                }
            });
    // Set delegate to obtain the render info
    previewOptions.setPreviewPageRender(
            new IPreviewPageRender() {
                @Override
                public void previewPageRender(PageRenderInfo pageRenderInfo) {
                    renderInfo[0] = pageRenderInfo;
                }
            });
    // Set PNG as an output image format
    previewOptions.setPreviewFormat(PreviewFormats.Png);
    // Set DPI for the output image
    previewOptions.setDpi(72);
    // Generate previews
    parser.generatePreview(previewOptions);
}

private static String getOutputPath(PageRenderInfo renderInfo, int pageNumber) throws java.io.IOException {
    // Set the file name. If the render info is set, then tile name is {Row}x{Column}.png
    String fileName = renderInfo == null
            ? String.format("preview_%d.png", pageNumber)
            : String.format("%d\\%dx%d.png", renderInfo.getPageNumber(), renderInfo.getRow(pageNumber), renderInfo.getColumn(pageNumber));
    return Constants.getOutputFilePath(fileName);
}

More resources

GitHub examples

You may easily run the code above and see the feature in action in our GitHub examples:

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