BufferedImage rotated, change resulting background

问题

When I rotate an image using Graphics2D.rotate() obviously it leaves some empty space in the corners. The empty corners become transparents.

I want my program to rotate the BufferedImage and to fill the remaining empty corners with a white color.

How do I do this?

In other words, I want to rotate the image while preserving a white background for the whole image.

This is my function:

public BufferedImage rotateImage(BufferedImage image, double degreesAngle) {    
        int w = image.getWidth();    
        int h = image.getHeight();    
        BufferedImage result = new BufferedImage(w, h, image.getType());  
        Graphics2D g2 = result.createGraphics();  
        g2.rotate(Math.toRadians(degreesAngle), w/2, h/2);
        g2.drawImage(image,null,0,0);  
        return result;   
    }    

I then use this image to paint it a transparent JPanel, which I later add to a JLayeredPane.

However, my image has transparent corners and I want to fill them with a white color.

回答1:

You have (at least) two options...

You Could...

Paint the background of the BufferedImage before you paint the rotated image...

public BufferedImage rotateImage(BufferedImage image, double degreesAngle) {    
    int w = image.getWidth();    
    int h = image.getHeight();    
    BufferedImage result = new BufferedImage(w, h, image.getType());  
    Graphics2D g2 = result.createGraphics();  
    g2.setColor(Color.WHITE);
    g2.fillRect(0, 0, w, h);
    g2.rotate(Math.toRadians(degreesAngle), w/2, h/2);
    g2.drawImage(image,null,0,0);  
    return result;   
}  

You Could...

Paint the area behind the image before you paint it to the panel...

来源：https://stackoverflow.com/questions/20256183/bufferedimage-rotated-change-resulting-background