iago-suarez · July 9, 2025 01:49 · Jan 4, 2017 · Jan 4, 2017 · Jan 4, 2017 · Jan 4, 2017
diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -6,6 +6,7 @@ The first step in order to be able to execute the [tutorial example](https://git
 ```bash
 # Export your NDK, it will be looked for OpenCV to compile your project. In my case
 export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
+
 # Download the necessary code
 cd graffter/libs/
 mkdir contrib_release_armv7a && contrib_release_armv7a

diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -4,6 +4,8 @@ The tutorial [Use OpenCL in Android camera preview based CV application](http://
 The first step in order to be able to execute the [tutorial example](https://github.com/opencv/opencv/tree/73a8fa8e6e50660a671620563156b8d7cddecf82/samples/android/tutorial-4-opencl) is to re-compile opencv with the correct flags:
 
 ```bash
+# Export your NDK, it will be looked for OpenCV to compile your project. In my case
+export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
 # Download the necessary code
 cd graffter/libs/
 mkdir contrib_release_armv7a && contrib_release_armv7a
@@ -44,10 +46,6 @@ make -j8
 adb install samples/android/tutorial-4-opencl/.build/bin/example-tutorial-4-opencl-debug.apk
 ```
 Notes:
-* I've previous exported the ANDROID_NDK as:
-```
-export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
-```
 * Here I'm compiling with the contrib modules, but if you don't need them just remove the line "-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \"
 * Here I'm only building the library for ARMv7a devices with NEON support, but you should add other architectures in the string. The full list is:
 

diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -45,9 +45,9 @@ adb install samples/android/tutorial-4-opencl/.build/bin/example-tutorial-4-open
 ```
 Notes:
 * I've previous exported the ANDROID_NDK as:
-  
-    export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
-
+```
+export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
+```
 * Here I'm compiling with the contrib modules, but if you don't need them just remove the line "-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \"
 * Here I'm only building the library for ARMv7a devices with NEON support, but you should add other architectures in the string. The full list is:
 

diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -45,7 +45,9 @@ adb install samples/android/tutorial-4-opencl/.build/bin/example-tutorial-4-open
 ```
 Notes:
 * I've previous exported the ANDROID_NDK as:
-  export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
+
+    export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
+
 * Here I'm compiling with the contrib modules, but if you don't need them just remove the line "-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \"
 * Here I'm only building the library for ARMv7a devices with NEON support, but you should add other architectures in the string. The full list is:
 

diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -44,6 +44,8 @@ make -j8
 adb install samples/android/tutorial-4-opencl/.build/bin/example-tutorial-4-opencl-debug.apk
 ```
 Notes:
+* I've previous exported the ANDROID_NDK as:
+  export ANDROID_NDK=~/graffter/libs/android-ndk-r10d/
 * Here I'm compiling with the contrib modules, but if you don't need them just remove the line "-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \"
 * Here I'm only building the library for ARMv7a devices with NEON support, but you should add other architectures in the string. The full list is:
 

diff --git a/opencv-opencl-android.md b/opencv-opencl-android.md
@@ -1,3 +1,4 @@
+# Setting Up OpenCL for OpenCV on Android, the full story 
 The tutorial [Use OpenCL in Android camera preview based CV application](http://docs.opencv.org/trunk/d7/dbd/tutorial_android_ocl_intro.html) show us how we can use the Transparent API to dramatically increase the performance of some expensive operations. 
 
 The first step in order to be able to execute the [tutorial example](https://github.com/opencv/opencv/tree/73a8fa8e6e50660a671620563156b8d7cddecf82/samples/android/tutorial-4-opencl) is to re-compile opencv with the correct flags:

diff --git a/gistfile1.txt → opencv-opencl-android.md b/gistfile1.txt → opencv-opencl-android.md
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,51 @@
+The tutorial [Use OpenCL in Android camera preview based CV application](http://docs.opencv.org/trunk/d7/dbd/tutorial_android_ocl_intro.html) show us how we can use the Transparent API to dramatically increase the performance of some expensive operations. 
+
+The first step in order to be able to execute the [tutorial example](https://github.com/opencv/opencv/tree/73a8fa8e6e50660a671620563156b8d7cddecf82/samples/android/tutorial-4-opencl) is to re-compile opencv with the correct flags:
+
+```bash
+# Download the necessary code
+cd graffter/libs/
+mkdir contrib_release_armv7a && contrib_release_armv7a
+git clone [email protected]:opencv/opencv.git
+mv opencv opencv-3.1.0
+git clone [email protected]:opencv/opencv_contrib.git
+
+# Creating our custom OpenCL SDK
+export OPENCL_SDK=~/graffter/libs/MotoX_OpenCL_SDK
+mkdir $OPENCL_SDK && cd $OPENCL_SDK
+mkdir lib include
+# Copy the OpenCL headers used to compile OpenCV 
+cp -r ~/graffter/libs/opencv-3.1.0/3rdparty/include/opencl/1.2/CL/ include/
+# Download the multiplattaform version of the C++ OpenCL Wrapper
+cd include/CL/ && wget https://www.khronos.org/registry/cl/api/1.2/cl.hpp && cd ../..
+# Connect you OpenCL supported android device and use adb to get the library 
+adb pull /system/vendor/lib/libOpenCL.so lib
+# Set the folder where we are going to compile opencv, it will be used when we run the ndk-build of the project
+export OPENCV_ANDROID_SDK=~/graffter/libs/contrib_release_armv7a
+cd $OPENCV_ANDROID_SDK
+
+# Now configure and compile opencv
+cmake -Wno-dev \
+-DCMAKE_TOOLCHAIN_FILE=../opencv-3.1.0/platforms/android/android.toolchain.cmake \
+-DANDROID_ABI="armeabi-v7a with NEON" \
+-DCMAKE_BUILD_WITH_INSTALL_RPATH=ON \
+-DBUILD_ANDROID_EXAMPLES=ON \
+-DINSTALL_ANDROID_EXAMPLES=ON \
+-DWITH_OPENCL=YES \
+-DANDROID_OPENCL_SDK=$OPENCL_SDK \
+-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \
+-DANDROID_NATIVE_API_LEVEL=14 \
+-DANDROID_SDK_TARGET=24 \
+../opencv-3.1.0
+make -j8
+
+# Now you would be able to install the generated APK with:
+adb install samples/android/tutorial-4-opencl/.build/bin/example-tutorial-4-opencl-debug.apk
+```
+Notes:
+* Here I'm compiling with the contrib modules, but if you don't need them just remove the line "-DOPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules \"
+* Here I'm only building the library for ARMv7a devices with NEON support, but you should add other architectures in the string. The full list is:
+
+> armeabi-v7a; armeabi; armeabi-v7a with NEON; armeabi-v7a-hard with NEON; armeabi-v7a with VFPV3; armeabi-v6 with VFP; arm64-v8a x86 x86_64 mips mips64"
+
+* **-DANDROID_NATIVE_API_LEVEL=14** Is necessary because lower API_LEVEL will cause problems compiling the tutorial-4-opencl [here](https://github.com/opencv/opencv/blob/fbf2383d5dfffeb7c60748be310f86327fb4a335/samples/android/tutorial-4-opencl/CMakeLists.txt#L7).