图片水印的生成方法

生成水印的过程。其实分为三个环节：第一，载入原始图片；第二，载入水印图片；第三，保存新的图片。

* /**
*     * create the bitmap from a byte array
*     *
*     * @param src the bitmap object you want proecss
*     * @param watermark the water mark above the src
*     * @return return a bitmap object ,if paramter's length is 0,return null
*     */
*    private Bitmap createBitmap( Bitmap src, Bitmap watermark )
*    {
*        String tag = "createBitmap";
*        Log.d( tag, "create a new bitmap" );
*        if( src == null )
*        {
*            return null;
*        }
*
*        int w = src.getWidth();
*        int h = src.getHeight();
*        int ww = watermark.getWidth();
*        int wh = watermark.getHeight();
*        //create the new blank bitmap
*        Bitmap newb = Bitmap.createBitmap( w, h, Config.ARGB_8888 );//创建一个新的和SRC长度宽度一样的位图
*        Canvas cv = new Canvas( newb );
*        //draw src into
*        cv.drawBitmap( src, 0, 0, null );//在 0，0坐标开始画入src
*        //draw watermark into
*        cv.drawBitmap( watermark, w - ww + 5, h - wh + 5, null );//在src的右下角画入水印
*        //save all clip
*        cv.save( Canvas.ALL_SAVE_FLAG );//保存
*        //store
*        cv.restore();//存储
*        return newb;
*    }