android生成圆形头像

public static Bitmap getRoundedCornerBitmap(Bitmap bitmap) {

        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final Paint paint = new Paint();
        //保证是方形，并且从中心画
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();
        int w;
        int deltaX = 0;
        int deltaY = 0;
        if (width <= height) {
            w = width;
            deltaY = height - w;
        } else {
            w = height;
            deltaX = width - w;
        }
        final Rect rect = new Rect(deltaX, deltaY, w, w);
        final RectF rectF = new RectF(rect);

        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        //圆形，所有只用一个

        int radius = (int) (Math.sqrt(w * w * 2.0d) / 2);
        canvas.drawRoundRect(rectF, radius, radius, paint);

        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }