在黑色/白色背景上旋转的图形2D

Question

I have a function that draws a rotated picture on a g2 component but for some reason I can't give it any colored background... I was trying to use methods .setColor() and .setBackground() but with no use. I have seen a similiar case here Graphics2D: Drawing black on white? but it didn't really help. Here is my function:

        public void rotateImage1(double degrees, ImageObserver o){

        double sin = Math.abs(Math.sin(Math.toRadians(degrees)));
        double cos = Math.abs(Math.cos(Math.toRadians(degrees)));
        ImageIcon icon = new ImageIcon(this.spiral);
        int w = icon.getIconWidth();
        int h = icon.getIconHeight();
        int neww = (int)Math.floor(w*cos+h*sin);
        int newh = (int)Math.floor(h*cos+w*sin);
        BufferedImage blankCanvas = new BufferedImage(neww, newh, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2 = (Graphics2D)blankCanvas.getGraphics();
        if(PhotoEdit.black)
            g2.setColor(Color.BLACK);
        else
            g2.setColor(Color.WHITE);
        g2.translate((neww-w)/2, (newh-h)/2);
        g2.rotate(Math.toRadians(degrees), icon.getIconWidth()/2, icon.getIconHeight()/2);

        g2.drawImage(this.spiral, 0, 0, o);
        this.spiral = blankCanvas;
}

PhotoEdit.black is a boolean variable that is true if the user selected the checkbox with black background option.

Answer 1

You are setting the color in graphics, but you aren't drawing it to the panel.

You can use g2.setColor(...) and g2.fillRect(...) and specify coordinates that cover the whole panel, and then draw your image on top.

Docs for fillRect: http://docs.oracle.com/javase/7/docs/api/java/awt/Graphics.html#fillRect%28int,%20int,%20int,%20int%29