How can I convert a BufferedImage object into an InputStream or a BLOB?

How can I do this without losing the original image format or quality?

You need to save it using some appropriate (lossless) format. The png format is one option.

The ImageIO class has methods for writing out an image to an output stream.

Here's a complete example of how you get hold of an InputStream from which you can read the PNG-representation of the content of a BufferedImage:

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bufferedImage, "png", baos);
InputStream is = new ByteArrayInputStream(baos.toByteArray());

Write functions to serialize/unserialize the BufferedImage to/from a byte [] and use classes ByteArrayInputStream and ByteArrayOutputStream.

You probably need to serialize the image type, width, height and the image pixel values (obtained with BufferedImage.getRGB(x, y)).

The alternative is to call ImageIO.write(image, "png", outStream) to convert the image to PNG format and write it to a ByteArrayOutputStream. There is an equivalent ImageIO.read(inputStream) method to read the image from a ByteArrayInputStream. There is some processing overhead in converting to/from PNG. But PNG is a compressed image format and you will save a lot of space compared with storing the images uncompressed.