How to get an InputStream from a BufferedImage?

Question

How can I get an InputStream from a BufferedImage object? I tried this but ImageIO.createImageInputStream() always returns NULL

BufferedImage bigImage = GraphicsUtilities.createThumbnail(ImageIO.read(file), 300);
ImageInputStream bigInputStream = ImageIO.createImageInputStream(bigImage);

The image thumbnail is being correctly generated since I can paint bigImage to a JPanel with success.

Answer 1

From http://usna86-techbits.blogspot.com/2010/01/inputstream-from-url-bufferedimage.html

It works very fine!

Here is how you can make an InputStream for a BufferedImage:

URL url = new URL("http://www.google.com/intl/en_ALL/images/logo.gif");
BufferedImage image = ImageIO.read(url);
ByteArrayOutputStream os = new ByteArrayOutputStream();
ImageIO.write(image, "gif", os);
InputStream is = new ByteArrayInputStream(os.toByteArray());

Answer 2

If you are trying to save the image to a file try:

ImageIO.write(thumb, "jpeg", new File(....));

If you just want at the bytes try doing the write call but pass it a ByteArrayOutputStream which you can then get the byte array out of and do with it what you want.

Answer 3

By overriding the method toByteArray(), returning the buf itself (not copying), you can avoid memory related problems. This will share the same array, not creating another of the correct size. The important thing is to use the size() method in order to control the number of valid bytes into the array.

final ByteArrayOutputStream output = new ByteArrayOutputStream() {
    @Override
    public synchronized byte[] toByteArray() {
        return this.buf;
    }
};
ImageIO.write(image, "png", output);
return new ByteArrayInputStream(output.toByteArray(), 0, output.size());