Android画图并保存图片的具体实现代码

/**
    * 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; 
   } 

/**
    * lessen the bitmap
    *
    * @param src bitmap
    * @param destWidth the dest bitmap width
    * @param destHeigth
    * @return new bitmap if successful ,oherwise null
    */ 
   private Bitmap lessenBitmap( Bitmap src, int destWidth, int destHeigth ) 
   { 
       String tag = "lessenBitmap"; 
       if( src == null ) 
       { 
           return null; 
       } 
       int w = src.getWidth();//源文件的大小 
       int h = src.getHeight(); 
       // calculate the scale - in this case = 0.4f 
       float scaleWidth = ( ( float ) destWidth ) / w;//宽度缩小比例 
       float scaleHeight = ( ( float ) destHeigth ) / h;//高度缩小比例 
       Log.d( tag, "bitmap width is :" + w ); 
       Log.d( tag, "bitmap height is :" + h ); 
       Log.d( tag, "new width is :" + destWidth ); 
       Log.d( tag, "new height is :" + destHeigth ); 
       Log.d( tag, "scale width is  :" + scaleWidth ); 
       Log.d( tag, "scale height is  :" + scaleHeight ); 
       Matrix m = new Matrix();//矩阵 
       m.postScale( scaleWidth, scaleHeight );//设置矩阵比例 
       Bitmap resizedBitmap = Bitmap.createBitmap( src, 0, 0, w, h, m, true );//直接按照矩阵的比例把源文件画入进行 
       return resizedBitmap; 
   }