Question

So, I have been modding Minecraft for a while, and I saw how it generates its buttons. It takes a very wide image of a button, takes part of the left, takes part of the right side, and puts the two back together to form a smaller image.

I’m sorry, but I can’t explain this well in words, so let me just show you with bad Paint.Net skills:

However, I cannot get it to work, as it turns out like this:

Here is part of my code:

public class ComponentToolbarButton extends JComponent implements MouseListener {

    private static final int HEIGHT = 40;

    // ... other methods here

    private BufferedImage getImageBasedOnWidth(Graphics g) {
        BufferedImage finalImage = null;
        BufferedImage rawImage = null;


         // Try/catch block to initialize rawImage

         // Setting font and things here        

        int compWidth = determineComponentWidth(g); // Returns the (should-be) width of the component

        if (compWidth != getWidth()) { 
            setPreferredSize(new Dimension(compWidth, HEIGHT)); // Just making sure :)
        }

        finalImage = new BufferedImage(compWidth, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics finalImageGraphics = finalImage.getGraphics();


        // Draw left side:
        finalImageGraphics.drawImage(rawImage, 0, 0, 0, compWidth / 2, 0, 0, compWidth, HEIGHT, null);

        // Draw right side:
        finalImageGraphics.drawImage(rawImage, compWidth / 2, 0, compWidth, HEIGHT, rawImage.getWidth() / 2 - compWidth,
            0, rawImage.getWidth(), rawImage.getHeight(), null);


        return finalImage;
    }
}

Thanks in advance! (I tried to shorten the code as much as I could BTW)

Answer 1

Okay, after some thinking, I came up with this little hack to demonstrate how I believe it should work 😛

public class TestMenu extends JComponent {

    protected static final int MAX_HEIGHT = 40;
    protected static final int LEFT_MARGIN = 5;
    protected static final int RIGHT_MARGIN = 5;

    protected static final ImageIcon BACKGROUND = new ImageIcon(TestMenu.class.getResource("/Menu.png"));

    private String text;

    public TestMenu() {

        setOpaque(false);
        text  = "This is some text";
        setFont(UIManager.getFont("Label.font"));

    }

    @Override
    public Dimension getPreferredSize() {

        FontMetrics fm = getFontMetrics(getFont());
        int width = fm.stringWidth(text) + LEFT_MARGIN + RIGHT_MARGIN;

        Dimension size = new Dimension(width, MAX_HEIGHT);

        return size;

    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        int width = getWidth() - 1;
        int height = getHeight() - 1;

        BufferedImage imgLeft = new BufferedImage(LEFT_MARGIN, MAX_HEIGHT, BufferedImage.TYPE_INT_ARGB);
        BufferedImage imgRight = new BufferedImage(RIGHT_MARGIN, MAX_HEIGHT, BufferedImage.TYPE_INT_ARGB);
        BufferedImage imgBody = new BufferedImage(width - LEFT_MARGIN - RIGHT_MARGIN, MAX_HEIGHT, BufferedImage.TYPE_INT_ARGB);

        Graphics2D g2d = imgLeft.createGraphics();
        g2d.drawImage(BACKGROUND.getImage(), 0, 0, this);
        g2d.dispose();

        g2d = imgRight.createGraphics();
        g2d.drawImage(BACKGROUND.getImage(), RIGHT_MARGIN - BACKGROUND.getIconWidth(), 0, this);
        g2d.dispose();

        g2d = imgBody.createGraphics();
        g2d.drawImage(BACKGROUND.getImage(), -LEFT_MARGIN, 0, this);
        g2d.dispose();

        g2d = (Graphics2D) g;

        g2d.drawImage(imgLeft, 0, 0, this);
        g2d.drawImage(imgBody, LEFT_MARGIN, 0, this);
        g2d.drawImage(imgRight, width - RIGHT_MARGIN, 0, this);

        FontMetrics fm = g2d.getFontMetrics();

        int x = (width - fm.stringWidth(text)) / 2;
        int y = ((height - fm.getHeight()) / 2) + fm.getAscent();

        g2d.setColor(Color.WHITE);
        g2d.drawString(text, x, y);


    }

}

First, one should never try and build all the image segments in the paint method, it will slow down the paint routine and consume to much memory, but for this example, I just wanted to demonstrate the idea. Use a backing buffer instead (which I think is what you were trying to do anyway).

This will produce this: