Itext PDF image black background

Question

I am using itext 5.5.13 to resize images in my pdf. I'm basically following the steps in Chapter 16's ResizeImage.java.

However, for certain PDF files I get a black background for my image. Is this a normal thing, and is there a way to prevent getting black backgrounds?

I tried to extract the image with itext also, and the image appears to have a black background too. This is confusing me, because the original PDF did not have a black background for the image.

I followed the code from this question to extract the image.

How to extract images from a PDF with iText in the correct order?

Here is my code: https://pastebin.com/hN6CTCRP

   public static void resizePdf() throws DocumentException, IOException {

    String src = "input.pdf";
    String dest = "output.pdf";

    PdfReader reader = new PdfReader(src);
    int n = reader.getXrefSize();
    PdfObject object;
    PRStream stream;
    // Look for image and manipulate image stream
    for (int i = 0; i < n; i++) {
        object = reader.getPdfObject(i);
        if (object == null || !object.isStream())
            continue;
        stream = (PRStream) object;
        if (!PdfName.IMAGE.equals(stream.getAsName(PdfName.SUBTYPE)))
            continue;
        if (!PdfName.DCTDECODE.equals(stream.getAsName(PdfName.FILTER)))
            continue;

        PdfImageObject image = new PdfImageObject(stream);
        BufferedImage bi = image.getBufferedImage();

        double factor = .5;

        if (bi == null)
            continue;
        int width = (int) (bi.getWidth() * factor);
        int height = (int) (bi.getHeight() * factor);
        if (width <= 0 || height <= 0)
            continue;
        BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        AffineTransform at = AffineTransform.getScaleInstance(factor, factor);
        Graphics2D g = img.createGraphics();
        g.drawRenderedImage(bi, at);

        System.out.println(image.getFileType());
        ByteArrayOutputStream imgBytes = new ByteArrayOutputStream();
        ImageIO.write(img, image.getFileType(), imgBytes);
        stream.clear();
        stream.setData(imgBytes.toByteArray(), false, PRStream.NO_COMPRESSION);
        stream.put(PdfName.TYPE, PdfName.XOBJECT);
        stream.put(PdfName.SUBTYPE, PdfName.IMAGE);
        stream.put(PdfName.FILTER, PdfName.DCTDECODE);
        stream.put(PdfName.WIDTH, new PdfNumber(width));
        stream.put(PdfName.HEIGHT, new PdfNumber(height));
        stream.put(PdfName.BITSPERCOMPONENT, new PdfNumber(8));
        stream.put(PdfName.COLORSPACE, PdfName.DEVICERGB);
    }
    reader.removeUnusedObjects();
    // Save altered PDF
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.setFullCompression();
    stamper.close();
    reader.close();
}