本文转载于
http://blog.csdn.net/u013096866/article/details/44516163
http://blog.csdn.net/csh159/article/details/8835477
http://blog.csdn.net/hezhipin610039/article/details/7899248/

1、获取资源文件 r.drawable中的图片转换为drawable、bitmap的4种方法
下面代码来源于：http://blog.csdn.net/u013096866/article/details/44516163
1）、
Resources resources = mContext.getResources();
Drawable drawable = resources.getDrawable(R.drawable.a);

2）、
Resources r = this.getContext().getResources();
Inputstream is = r.openRawResource(R.drawable.my_background_image);
BitmapDrawable bmpDraw = new BitmapDrawable(is);
Bitmap bmp = bmpDraw.getBitmap();

3）、
Bitmap bmp=BitmapFactory.decodeResource(r, R.drawable.icon);
Bitmap newb = Bitmap.createBitmap( 300, 300, Config.ARGB_8888 );

4）、
InputStream is = getResources().openRawResource(R.drawable.icon);
Bitmap mBitmap = BitmapFactory.decodeStream(is);

2、Bitmap与string的互转
下面代码来源于：http://blog.csdn.net/csh159/article/details/8835477
/**
* 图片转成string
*
* @param bitmap
* @return
*/
public static String convertIconToString(Bitmap bitmap)
{
ByteArrayOutputStream baos = new ByteArrayOutputStream();// outputstream
bitmap.compress(CompressFormat.PNG, 100, baos);
byte[] appicon = baos.toByteArray();// 转为byte数组
return Base64.encodeToString(appicon, Base64.DEFAULT);

    }  
  
    /**  
     * string转成bitmap  
     *   
     * @param st  
     */  
    public static Bitmap convertStringToIcon(String st)  
    {  
        // OutputStream out;  
        Bitmap bitmap = null;  
        try  
        {  
            // out = new FileOutputStream("/sdcard/aa.jpg");  
            byte[] bitmapArray;  
            bitmapArray = Base64.decode(st, Base64.DEFAULT);  
            bitmap =  
                    BitmapFactory.decodeByteArray(bitmapArray, 0,  
                            bitmapArray.length);  
            // bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);  
            return bitmap;  
        }  
        catch (Exception e)  
        {  
            return null;  
        }  
    }  

3、 Bitmap和Drawable相互转换的方法
下面代码来源于：http://blog.csdn.net/hezhipin610039/article/details/7899248/
1)、Bitmap---->Drawable
Drawable drawable =new BitmapDrawable(bmp);

2)、Drawable → Bitmap
public static Bitmap drawableToBitmap(Drawable drawable) {
Bitmap bitmap = Bitmap.createBitmap(
drawable.getIntrinsicWidth(),
drawable.getIntrinsicHeight(),
drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888: Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
//canvas.setBitmap(bitmap);
drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
drawable.draw(canvas);
return bitmap;
}

3）、Bitmap → byte[]
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
baos.toByteArray();

4）、 byte[] → Bitmap
private Bitmap Bytes2Bimap(byte[] b){
if(b.length!=0){
return BitmapFactory.decodeByteArray(b, 0, b.length);
}
else {
return null;
}
}