Android - как масштабировать изображение при прокрутке NestedScrollView?

Попробуй это

<android.support.design.widget.CoordinatorLayout 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"
    android:fitsSystemWindows = "true">

    <android.support.design.widget.AppBarLayout
        android:id = "@+id/appBarLayout"
        android:layout_width = "match_parent"
        android:layout_height = "wrap_content"
        android:elevation = "8dp"
        android:fitsSystemWindows = "true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width = "match_parent"
            android:id = "@+id/collapsingToolbarLayout"
            android:layout_height = "match_parent"
            android:fitsSystemWindows = "true"
            app:contentScrim = "?colorPrimary"
            app:expandedTitleTextAppearance = "@style/TextAppearance.AppCompat.Title"
            app:layout_scrollFlags = "exitUntilCollapsed|scroll"
            app:titleEnabled = "false">

            <ImageView
                android:id = "@+id/bg"
                android:layout_width = "match_parent"
                android:layout_height = "220dp"
                android:scaleType = "centerCrop"
                android:src = "@color/colorPrimaryDark"
                app:layout_collapseMode = "pin" />

            <android.support.v7.widget.Toolbar
                android:id = "@+id/polygon_toolbar"
                android:layout_width = "match_parent"
                android:layout_height = "?attr/actionBarSize"
                app:contentInsetStartWithNavigation = "0dp"
                app:layout_collapseMode = "pin" />
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <de.hdodenhof.circleimageview.CircleImageView
        android:id = "@+id/imageView"
        android:layout_width = "96dp"
        android:layout_height = "96dp"
        android:src = "@drawable/abc"
        android:animateLayoutChanges = "true"
        app:layout_anchor = "@id/appBarLayout"
        app:layout_anchorGravity = "center|bottom" />
</android.support.design.widget.CoordinatorLayout>

Код активности

import android.os.Bundle;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CollapsingToolbarLayout;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.view.animation.ScaleAnimation;
import android.widget.ImageView;



public class MainActivity extends AppCompatActivity {


    ImageView imageView;
    CollapsingToolbarLayout collapsingToolbarLayout;
    AppBarLayout appBarLayout;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);



        collapsingToolbarLayout = findViewById(R.id.collapsingToolbarLayout);
        appBarLayout = findViewById(R.id.appBarLayout);
        imageView = findViewById(R.id.imageView);

        appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            boolean isShow = true;
            int scrollRange = -1;

            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                if (scrollRange == -1) {
                    scrollRange = appBarLayout.getTotalScrollRange();
                }
                if (scrollRange + verticalOffset == 0) {
                    isShow = true;
                    Animation animation = AnimationUtils.loadAnimation(MainActivity.this, R.anim.scale_down);
                    imageView.startAnimation(animation);
                    imageView.setVisibility(View.GONE);
                    //imageView.setVisibility(View.GONE);
                } else if (isShow) {
                    Animation animation = AnimationUtils.loadAnimation(MainActivity.this, R.anim.scale_up);
                    imageView.startAnimation(animation);
                    imageView.setVisibility(View.VISIBLE);
                    imageView.setVisibility(View.VISIBLE);
                    isShow = false;
                }
            }
        });

    }
    public void scaleView(View v, float startScale, float endScale) {
        Animation anim = new ScaleAnimation(
                1f, 1f, // Start and end values for the X axis scaling
                startScale, endScale, // Start and end values for the Y axis scaling
                Animation.RELATIVE_TO_SELF, 0f, // Pivot point of X scaling
                Animation.RELATIVE_TO_SELF, 1f); // Pivot point of Y scaling
        anim.setFillAfter(true); // Needed to keep the result of the animation
        anim.setDuration(1000);
        v.startAnimation(anim);
    }

}

Файл ANIMATION

scale_down

<set xmlns:android = "http://schemas.android.com/apk/res/android">
    <scale
        android:duration = "1000"
        android:fromXScale = "1.0"
        android:fromYScale = "1.0"
        android:pivotX = "50%"
        android:pivotY = "50%"
        android:toXScale = "0"
        android:toYScale = "0" />
</set>

scale_up

<set xmlns:android = "http://schemas.android.com/apk/res/android">
    <scale
        android:duration = "1000"
        android:fromXScale = "0"
        android:fromYScale = "0"
        android:pivotX = "50%"
        android:pivotY = "50%"
        android:toXScale = "1.0"
        android:toYScale = "1.0" />
</set>