老生常谈了，直接看代码。

bufferedp_w_picpath.getColorModel().getTransparency()以获得原始图片透明度用于生成缓存图，在缓存图进行相应操作即可。

/** *//**
     * 旋转图片为指定角度
     * 
     * @param bufferedp_w_picpath
     *            目标图像
     * @param degree
     *            旋转角度
     * @return
     */
    public static BufferedImage rotateImage(final BufferedImage bufferedp_w_picpath,
            final int degree) ...{
        int w = bufferedp_w_picpath.getWidth();
        int h = bufferedp_w_picpath.getHeight();
        int type = bufferedp_w_picpath.getColorModel().getTransparency();
        BufferedImage img;
        Graphics2D graphics2d;
        (graphics2d = (img = new BufferedImage(w, h, type))
                .createGraphics()).setRenderingHint(
                RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        graphics2d.rotate(Math.toRadians(degree), w / 2, h / 2);
        graphics2d.drawImage(bufferedp_w_picpath, 0, 0, null);
        graphics2d.dispose();
        return img;
    }

    /** *//**
     * 变更图像为指定大小
     * 
     * @param bufferedp_w_picpath
     *            目标图像
     * @param w
     *            宽
     * @param h
     *            高
     * @return
     */
    public static BufferedImage resizeImage(final BufferedImage bufferedp_w_picpath,
            final int w, final int h) ...{
        int type = bufferedp_w_picpath.getColorModel().getTransparency();
        BufferedImage img;
        Graphics2D graphics2d;
        (graphics2d = (img = createImage(w, h, type))
                .createGraphics()).setRenderingHint(
                RenderingHints.KEY_INTERPOLATION,
                RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        graphics2d.drawImage(bufferedp_w_picpath, 0, 0, w, h, 0, 0, bufferedp_w_picpath
                .getWidth(), bufferedp_w_picpath.getHeight(), null);
        graphics2d.dispose();
        return img;
    }

    /** *//**
     * 水平翻转图像
     * 
     * @param bufferedp_w_picpath 目标图像
     * @return
     */
    public static BufferedImage flipImage(final BufferedImage bufferedp_w_picpath) ...{
        int w = bufferedp_w_picpath.getWidth();
        int h = bufferedp_w_picpath.getHeight();
        BufferedImage img;
        Graphics2D graphics2d;
        (graphics2d = (img = createImage(w, h, bufferedp_w_picpath
                .getColorModel().getTransparency())).createGraphics())
                .drawImage(bufferedp_w_picpath, 0, 0, w, h, w, 0, 0, h, null);
        graphics2d.dispose();
        return img;
    }