如果通过网络加载了一张位图，想拿到这张位图的Bitmap，有两种办法，至于那种好，可能要看是在什么情况下了
1，根据已有的Drawable创建一个新的Bitmap:
private Bitmap bitmap;
private void drawableToBitamp(Drawable drawable)
{
int w = drawable.getIntrinsicWidth();
int h = drawable.getIntrinsicHeight();
System.out.println("Drawable转Bitmap");
Bitmap.Config config =
drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
bitmap = Bitmap.createBitmap(w,h,config);
//注意，下面三行代码要用到，否在在View或者surfaceview里的canvas.drawBitmap会看不到图
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, w, h);
drawable.draw(canvas);
}
2,直接从现有的Drawable中取出Bitmap:
private Bitmap bitmap;
private void drawableToBitamp(Drawable drawable)
{
BitmapDrawable bd = (BitmapDrawable) drawable;
bitmap = bd.getBitmap();
}
Drawable转换为Bitmap两种方法,布布扣,bubuko.com
原文：http://www.cnblogs.com/caicaixu/p/3737385.html