Convert PNG to PDF using Java

Convert-PNG-to-PDF.java

public static void ConvertImageToPDF(String inputFileName, String outputFileName) throws Exception {

    // Instantiate an instance of Document class  
    Document doc = new Document();
    // Create an object of DocumentBuilder class to make it simple to add content to the document.  
    DocumentBuilder builder = new DocumentBuilder(doc);

    // Load images from the disk using the appropriate reader.
    // The file formats that can be loaded depends on the image readers available on the machine.
    // Load the input image file by calling the createImageInputStream method and assign it to the object of ImageInputStream.
    ImageInputStream iis = ImageIO.createImageInputStream(new File(inputFileName));
    // Invoke the getImageReaders method that returns an Iterator containing all currently registered ImageReaders and assigns it to the object of ImageReader class.
    ImageReader reader = ImageIO.getImageReaders(iis).next();
    // Call the setInput method that sets the input source to use to the given ImageInputStream or other Object. 
    reader.setInput(iis, false);

    // Get the number of frames in the image by calling the getNumImages method  
    int framesCount = reader.getNumImages(true);

    // Loop through all frames.
    for (int frameIdx = 0; frameIdx < framesCount; frameIdx++) {
        // Insert a section break before each new page, in case of a multi-frame image.
        if (frameIdx != 0)
            builder.insertBreak(BreakType.SECTION_BREAK_NEW_PAGE);

        // Select active frame and assign it to the object of BufferedImage class 
        BufferedImage image = reader.read(frameIdx);

        // We want the size of the page to be the same as the size of the image.
	      // Convert pixels to points to size the page to the actual image size.
	      // Invoke the getPageSetup method to access current page setup and assign it to the object of the PageSetup class   
        PageSetup ps = builder.getPageSetup();
        // Set the page height by calling the setPageWidth method 
        ps.setPageWidth(ConvertUtil.pixelToPoint(image.getWidth()));
        // Invoke the setPageHeight method to set the width of the page 
        ps.setPageHeight(ConvertUtil.pixelToPoint(image.getHeight()));

        // Insert the image into the document and position it at the top left corner of the page by calling the insertImage method.
        builder.insertImage(
                image,
                RelativeHorizontalPosition.PAGE,
                0,
                RelativeVerticalPosition.PAGE,
                0,
                ps.getPageWidth(),
                ps.getPageHeight(),
                WrapType.NONE);
    }

    if (iis != null) {
        iis.close();
        reader.dispose();
    }
    // Save the file as a PDF file format by calling the save method
    doc.save(outputFileName);
}