Android TensorFlow Detect Object Example

A simple android using Tensor Flow and pre-trained model to detect objects captured from camera

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Let build Tensor Flow first

• Clone Tensor Flow source code from https://github.com/tensorflow/tensorflow.git
• Download NDK https://developer.android.com/ndk/downloads/older_releases.html#ndk-12b-downloads (should download revision 12b to build tensor flow without error)
• Instal Bazel, Bazel is the primary build system for TensorFlow. On Mac using homebrew for installing easily https://bazel.build/versions/master/docs/install-os-x.html
• Go to source code of Tensor Flow cloned above, open WORKSPACE file to edit. Uncomment android_sdk_repository and android_ndk_repository like this:

android_sdk_repository(
    name = "androidsdk",
    api_level = 23,
    build_tools_version = "25.0.2",
    # Replace with path to Android SDK on your system
    path = "/Android/sdk/",
)

android_ndk_repository(
    name="androidndk",
    path="/Android/android-ndk-r12b/",
    api_level=14)
    

• Build TensorFlow with Bazel, must go to folder of tensor flow source code to run this command

 
    bazel build -c opt //tensorflow/contrib/android:lib_tensorflow.so \
   --crosstool_top=//external:android/crosstool \
   --host_crosstool_top=@bazel_tools//tools/cpp:toolchain \
   --cpu=armeabi-v7a \
   --strategy=CppCompile=standalone
 

• When build finished successfully, you will find lib_tensorflow.so file in

 [tensorflow source code path]/bazel-bin/tensorflow/contrib/android/lib_tensorflow.so
 

• Now you need to generate jar file to import into android project, run this command

 bazel build //tensorflow/contrib/android:android_tensorflow_java
 

• So now you have android_tensorflow_java.jar in folder [tensorflow source code path]/bazel-bin/tensorflow/contrib/android/ and can add as library to android project, create jniLibs folder in src/main and copy lib_tensorflow.so to there.

• In this example will use the Google pre-trained model which does the object detection on a given image. Download here https://storage.googleapis.com/download.tensorflow.org/models/inception5h.zip . Then copy them to assest folder of android project.