Easiest XML-only solution I know to add a <ripple> to an <ImageView> (tested on API >= 21)

README.md

See the related Medium article for more info and a GIF showing the final result.

drawable_card_ripple.xml

<?xml version="1.0" encoding="utf-8"?>
<ripple
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:color="?colorControlHighlight">

    <item android:drawable="@drawable/card_image" />

</ripple>

layout_card.xml

<!-- ... -->

  <!-- We want to add a ripple to our image, but :
    * we can't use `foreground` since it isn't supported on APIs < 23
    * we can't wrap the image with a <ripple> and set it as the `background` cause in some
      cases the image is stretched, and it wouldn't be viable to hard-code the view's height ;
      so we need to use the `src` and `adjustViewBounds` attrs to get the right image size
    * if we use `src` and put the ripple as `background` it'll be drawn beneath it

    The solution I've found is to use `src` + `adjustViewBounds` to get the right view size,
    hide the `src` image by tinting it to transparent, and use `background` to show the same
    image wrapped in a <ripple> -->

  <ImageView
      android:adjustViewBounds="true"
      android:background="@drawable/card_ripple"
      android:layout_height="wrap_content"
      android:layout_width="wrap_content"
      android:src="@drawable/card_image"
      android:tint="@android:color/transparent"
      android:tintMode="src_in" />

<!-- ... -->