转载自http://cfanz.cn/index.php?c=article&a=read&id=141146

1、
Resources resources = mContext.getResources();
Drawable drawable = resources.getDrawable(R.drawable.a);
imageview.setBackground(drawable);

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);

Android 之 Bitmap 和 File 相互转换

try{
String filePath=”/storage/emulated/0/123.jpg"; 
Bitmap bitmap=BitmapFactory.decodeFile(filePath,getBitmapOption(2)); //将图片的长和宽缩小味原来的1/2
}catch(Exception e){
e.printStackTrace();
}

private Options getBitmapOption(int inSampleSize){ 
System.gc(); 
BitmapFactory.Options options = new BitmapFactory.Options(); 
options.inPurgeable = true; 
options.inSampleSize = inSampleSize; 
return options; 
}

Bitmap对象保存味图片文件

public void saveBitmapFile(Bitmap bitmap){ 
File file=new File(“/storage/emulated/0/1234.jpg”);//将要保存图片的路径 
  try { 
          BufferedOutputStream bos = new BufferedOutputStream(new     FileOutputStream(file)); 
          bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos); 
          bos.flush(); 
          bos.close(); 
    } catch (IOException e) { 
        e.printStackTrace(); 
    } 
}