base64转bitmap

怎么样把base64 的一长串代码转化成bitmap（安卓），每次转换都报错：java.lang.IllegalArgumentException: bad base-64
这是我的代码：
public static Bitmap stringtoBitmap(String string) {
Bitmap bitmap = null;
try {
byte[] bitmapArray;
bitmapArray = Base64.decode(string, Base64.DEFAULT);
bitmap = BitmapFactory.decodeByteArray(bitmapArray, 0, bitmapArray.length);
} catch (Exception e) {
e.printStackTrace();
}
return bitmap;
}
我传参数就是在网上用图片生成的base64字符串，具体格式如下：
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAASwAAAEsCAYAAAB5fY51AAAABHNCSVQICAgIfAhkiAAAAAlwSFlzAAASdAAAEnQB3mYfeAAAIABJREFUeJzsvXmcXUWZ//95qu........GP4/AM6F2NNgroAAAAAASUVORK5CYII=
我去掉最前面的data:image/png;base64,再传入也不行，始终报上面那个错误，求大神指导！！收起就是怎么把data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAASwAAAEsCAYAAAB5fY51AAAABHNCSVQICAgIfAhkiAAAAAlwSFlzAAASdAAAEnQB3mYfeAAAIABJREFUeJzsvXmcXUWZ//95qu........GP4/AM6F2NNgroAAAAAASUVORK5CYII=
这样的一串转化为bitmap？？？