android :RadioButton 加载图片过大问题

RadioButton[] rb = new RadioButton[3];
rb[0] = rb_home;
rb[1] = rb_setting;
rb[2] = rb_me;
for(RadioButton r:rb){
Drawable[] drawables = r.getCompoundDrawables();
Rect rect = new Rect(0,0,drawables[1].getMinimumWidth()/3,drawables[1].getMinimumHeight()/3);
drawables[1].setBounds(rect);
r.setCompoundDrawables(null , drawables[1] , null ,null);
}