일반적인 이미지의 투명도를 조절하고 싶은데.. 

public void paint(Graphics g) {  
        screenImage = createImage(1280, 720);
        screenGraphic = screenImage.getGraphics();
        screenDraw(screenGraphic); 
        //g.drawImage(BG, 0, 0, null);
        g.drawImage(screenImage, 0, 0, null);
    }
    
    public void screenDraw(Graphics g) {
        g.drawImage(BG, 0, 0, null);  
        if(isMainScreen) {
            //g.drawImage(changedImageAlpha(selectedImage, 255), 130, 360, null);
            changedImageAlpha(selectedImage).drawImage(selectedImage, 120, 360, null);
            //g.drawImage(selectedImage, 120, 360, null);
        }
        paintComponents(g); 
        this.repaint();
    }
    
    public Graphics2D changedImageAlpha(Image image) {
        BufferedImage img = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB);
        Graphics2D g = img.createGraphics(); 
        Composite c = AlphaComposite.getInstance(AlphaComposite.SRC_ATOP, 0.5f); 
        g.setComposite(c); 
        g.drawImage(image, 0, 0, null);
        g.dispose();
        return g;
    }

selectedImage 표시가 안됩니다.