Transparent Scrollview over image very slow

Question

I tried to replicate this behaviour, but after implementing it I observed a large performance decrease.

Then I tried to implement it in a different way: I would put the image behind the scrollview, and simply give the contents of the scrollview some top padding. Here's some relevant XML:

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="">


    <ImageView
        android:id="@+id/profileImage"
        android:layout_width="0dp"
        android:layout_height="144dp"
        android:scaleType="centerCrop"
        android:src="@drawable/mapview"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ScrollView
        android:id="@+id/profileScrollView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginEnd="16dp"
            android:layout_marginStart="16dp"
            android:paddingBottom="70dp"
            android:paddingTop="120dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent">

        </android.support.constraint.ConstraintLayout>
    </ScrollView>
</android.support.constraint.ConstraintLayout>

I left out unnecessary XML.

This poor performance happens when the ScrollView tries to move over an ImageView. It still happens if the ImageView is embedded in another view, like a ConstraintLayout.

Why is this ScrollView slow? Am I supposed to change something in my layout? Thanks!