Display image from 2D array data in java

Question

I have some data that is loaded from the text file that corresponds to my image file. this data is now in a 2D array. I want to show this image. apparently the image show be of format bufferedimage. but mine is just simple 2D double format. Also how is possible to resize the image, meaning to make it twice bigger ( requiring interpolation in between of course)

In other words how can we do the "imshow" and " imresize" Matlab equilvalent in java?

Answer 1

There is no simple method for converting between an array based intensity matrix to a renderable image in Java, at least not that I am aware of. Nor is there any simple one line method for displaying an image on the screen etc.

It is however correct that a BufferedImage would be a viable solution in this case. What you would have to do is to create a BufferedImage of the desired size and then loop through your 2D intensity matrix and fill in the colors in the resulting image.

Once you have the data in form of a BufferedImage you can use it directly for rendering. For example you could create a JFrame with a custom JPanel component for displaying the image. The following sample code illustrates that procedure: (Note that this assumes that your image data in the 2D array is scaled to fit in the interval [0,1]. If it is not then it will have to be re-scaled prior to filling in the BufferedImage.)

public class ImageTest {

    private static final int HEIGHT = 250;
    private static final int WIDTH = 250;

    public static void main(String[] args) {
        double[][] data = new double[WIDTH][HEIGHT];
        Random r = new Random();
        for(int i = 0; i < WIDTH; i++) {
            for(int j = 0; j < HEIGHT; j++) {
                data[i][j] = r.nextDouble();
            }
        }

        final BufferedImage img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = (Graphics2D)img.getGraphics();
        for(int i = 0; i < WIDTH; i++) {
            for(int j = 0; j < HEIGHT; j++) {
                float c = (float) data[i][j];
                g.setColor(new Color(c, c, c));
                g.fillRect(i, j, 1, 1);
                data[i][j] = r.nextDouble();
            }
        }

        JFrame frame = new JFrame("Image test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JPanel panel = new JPanel() {
            @Override
            protected void paintComponent(Graphics g) {
                Graphics2D g2d = (Graphics2D)g;
                g2d.clearRect(0, 0, getWidth(), getHeight());
                g2d.setRenderingHint(
                        RenderingHints.KEY_INTERPOLATION,
                        RenderingHints.VALUE_INTERPOLATION_BILINEAR);
                        // Or _BICUBIC
                g2d.scale(2, 2);
                g2d.drawImage(img, 0, 0, this);
            }
        };
        panel.setPreferredSize(new Dimension(WIDTH*2, HEIGHT*2));
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true);
    }
}

If you are happy with resizing and interpolating in the resulting output image then you can achieve it by simply scaling the graphics context and enabling the interpolation rendering hint on it, as the above example shows when displaying/rendering the image. (This can of course be done directly in the BufferedImage as well in a similar fashion.

Answer 2

Have a look at MemoryImageSource. It might not do exactly what you want (because Java tends to use int / byte for image data) but it will at least send you down the right route.

http://www.javaworld.com/javatips/jw-javatip16.html