Cannot rotate transparent image using swt Transform

I'm trying to rotate a PNG image on a canvas and the quality of the image becomes very bad after rotation. Initially the PNG is an arrow on a transparent background. After rotation it is impossible to tell that it开发者_运维知识库 is an arrow.

I use following code:

Transform oldTransform = new Transform(
Display.getCurrent());
gc.getTransform(oldTransform);

Transform transform = new Transform(Display.getCurrent());
transform.translate(xm + imageBounds.width / 2, ym + imageBounds.height / 2);
transform.rotate(179);
transform.translate(-xm - imageBounds.width / 2, -ym - imageBounds.height / 2);

gc.setTransform(transform);
gc.drawImage(image, xm, ym);
gc.setTransform(oldTransform);

transform.dispose();

Thank you in advance.

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Instead of rotating the image 180 degrees, you could flip it horizontally and vertically (without any pixel transformation):

private BufferedImage flipH(BufferedImage src) {
        int w = src.getWidth();  
        int h = src.getHeight();  
        BufferedImage dst = new BufferedImage(w, h, src.getType());
        Graphics2D g = dst.createGraphics();  
        g.drawImage(src,
                    0, // x of first corner  (destination)
                    0, // y of first corner  (destination)
                    w, // x of second corner (destination)
                    h, // y of second corner (destination)
                    w, // x of first corner  (source)
                    0, // y of first corner  (source)
                    0, // x of second corner (source)
                    h, // y of second corner (source)
                    null);  
        g.dispose();
        return dst;
}

private BufferedImage flipV(BufferedImage src) {
        int w = src.getWidth();  
        int h = src.getHeight();  
        BufferedImage dst = new BufferedImage(w, h, src.getType());
        Graphics2D g = dst.createGraphics();  
        g.drawImage(src, 0, 0, w, h, 0, h, w, 0, null);  
        g.dispose();
        return dst;
}

...
BufferedImage flipped = flipH(flipV(ImageIO.read(new File("test.png"))));
ImageIcon icon = new ImageIcon(flipped);
...

Edit: or even better, flip both horizontally and vertically in single op (same as rotating 180 degrees):

g.drawImage(src, 0, 0, w, h, w, h, 0, 0, null);  

Edit2: There is also SWT-specific example of image rotation/flipping without Transform too.