How to resize image of checkbox in android?

I am adding image for checkbox widget (that is instead of default i am adding my own image for both clicked and unclciked in .xml file by using selector)its geting added but image is not able to resize to small,it stays in its original size.How could i make image to get small ?

the code used to create checkbox is

    <CheckBox
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/white"
            android:button="@drawable/check_box"
            android:drawablePadding="20dp"
            android:text="check box text"
            android:textColor="@color/labelColor" />