Camera and Camera2 preview is rendered via OpenGL textures and can be modified on CPU via C++ code. No OpenCL yet.

samples/android/tutorial-4-opencl/res/layout/activity.xml

@@ -0,0 +1,12 @@
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context="${relativePackage}.${activityClass}" >
+
+    <TextView
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/app_name" />
+
+</RelativeLayout>

samples/android/tutorial-4-opencl/res/values/strings.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+
+    <string name="app_name">OpenCV Tutorial 4 - Use OpenCL</string>
+
+</resources>