Compare PDF Documents in Java

Aspose.PDF for Java provides both side-by-side and graphical comparison APIs for detecting differences between PDF files.

Compare pages and export difference images

Use this example when you need image-based difference output for a specific pair of PDF pages.

1. Open both source PDF Document objects. «««< HEAD
2. Use GraphicalPdfComparer to get the page-level ImagesDifference. =======
3. Use ‘GraphicalPdfComparer’ to get the page-level ‘ImagesDifference’.

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1. Export the generated difference images and dispose the comparison result.

public static void comparePdfWithGetDifferenceMethod(
        Path inputFile1, Path inputFile2, Path diffOutputFile, Path destinationOutputFile) throws Exception {
    try (Document document1 = new Document(inputFile1.toString());
         Document document2 = new Document(inputFile2.toString())) {
        GraphicalPdfComparer comparer = new GraphicalPdfComparer();
        ImagesDifference imagesDifference = comparer.getDifference(document1.getPages().get_Item(1),
                document2.getPages().get_Item(1));

        ImageIO.write(imagesDifference.differenceToImage(Color.getRed(), Color.getWhite()),
                "png", diffOutputFile.toFile());
        ImageIO.write(imagesDifference.getDestinationImage(), "png", destinationOutputFile.toFile());
        imagesDifference.dispose();
    }
    System.out.println("Difference images saved to " + diffOutputFile + " and " + destinationOutputFile);
}

Compare specific pages side by side

Use this example when only selected pages should be compared and saved as a side-by-side PDF result.

1. Open both source PDF Document objects. «««< HEAD
2. Configure SideBySideComparisonOptions for the required comparison mode. =======
3. Configure ‘SideBySideComparisonOptions’ for the required comparison mode.

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1. Compare the selected pages and save the output PDF.

public static void comparingSpecificPages(Path inputFile1, Path inputFile2, Path outputFile) {
    try (Document document1 = new Document(inputFile1.toString());
         Document document2 = new Document(inputFile2.toString())) {
        SideBySideComparisonOptions options = new SideBySideComparisonOptions();
        options.setAdditionalChangeMarks(true);
        options.setComparisonMode(ComparisonMode.IgnoreSpaces);

        SideBySidePdfComparer.compare(document1.getPages().get_Item(1), document2.getPages().get_Item(1),
                outputFile.toString(), options);
    }
    System.out.println("Specific pages comparison saved to " + outputFile);
}

Compare full PDF documents graphically

This example generates a graphical PDF report that highlights visual differences across the entire documents.

1. Open both source PDF Document objects.
2. Configure the GraphicalPdfComparer threshold, color, and resolution.
3. Compare the full documents and save the graphical output PDF.

public static void comparePdfWithCompareDocumentsToPdfMethod(Path inputFile1, Path inputFile2, Path outputFile) {
    try (Document document1 = new Document(inputFile1.toString());
         Document document2 = new Document(inputFile2.toString())) {
        GraphicalPdfComparer pdfComparer = new GraphicalPdfComparer();
        pdfComparer.setThreshold(3.0);
        pdfComparer.setColor(Color.getBlue());
        pdfComparer.setResolution(new Resolution(300));
        pdfComparer.compareDocumentsToPdf(document1, document2, outputFile.toString());
    }
    System.out.println("Graphical comparison saved to " + outputFile);
}

Compare entire documents side by side

Use this example when the whole documents should be compared page by page in a side-by-side PDF output.

1. Open both source PDF Document objects.
2. Configure SideBySideComparisonOptions for the desired comparison behavior.
3. Compare the full documents and save the result as a PDF.

public static void comparingEntireDocuments(Path inputFile1, Path inputFile2, Path outputFile) {
    try (Document document1 = new Document(inputFile1.toString());
         Document document2 = new Document(inputFile2.toString())) {
        SideBySideComparisonOptions options = new SideBySideComparisonOptions();
        options.setAdditionalChangeMarks(true);
        options.setComparisonMode(ComparisonMode.IgnoreSpaces);

        SideBySidePdfComparer.compare(document1, document2, outputFile.toString(), options);
    }
    System.out.println("Entire document comparison saved to " + outputFile);
}