Shell file which handles everything related to building OpenALPR for Android (armeabi, armeabi-v7a, etc..). It installs Android SDK, NDK, CMAKE, JDK and wraps it into a single .sh file. Only tested on a specific Ubuntu version right now, but probably works on others aswell. Tested on Ubuntu 17.10 x64

KJPOpenALPRBuildAndroid.sh

#!/bin/bash

# Only tested on Ubuntu 17.10 x64 (This is because CMAKE Package 3.6 is required for Build OpenALPR Android Script)

########################################################################################################
# Script pieced together and tested by Kevin J. Petersen (Github: https://github.com/kevinjpetersen) ###
########################################################################################################

## Scripts used ##
# ubuntu-cli-install-android-sdk.sh by zhy0 (Github: https://github.com/zhy0)
# build_openalpr_android.sh by jav974 (Github: https://github.com/jav974)

# Steps:
# 1. Install CMAKE
# 2. Install OpenJDK
# 3. Run Android SDK and NDK with Script
# 4. Run Build OpenALPR Android Script

# Settings (Variables that need to be setuo)
SCRIPT=`realpath $0`
SCRIPTPATH=`dirname $SCRIPT`

# Cleans up if files already exists
rm -rf openalpr || true
rm -rf OpenCV-android-sdk || true
rm -rf tess2 || true
rm -rf android-sdk-linux || true
rm -rf android-ndk-r16b || true
rm -rf android-ndk-r16b-linux-x86_64.zip || true
rm -rf android-sdk_r24.4.1-linux.tgz || true

# Install CMAKE
sudo apt-get install cmake

# Install OpenJDK

sudo add-apt-repository ppa:openjdk-r/ppa
sudo apt-get update
sudo apt-get install openjdk-8-jdk

export PATH=$PATH:/usr/lib/jvm/java-8-openjdk-amd64/bin

# Install Android SDK Script

# Thanks to https://gist.github.com/wenzhixin/43cf3ce909c24948c6e7
# Execute this script in your home directory. Lines 17 and 21 will prompt you for a y/n

# Install Oracle JDK 8
add-apt-repository ppa:webupd8team/java
apt-get update
apt-get install -y oracle-java8-installer
apt-get install -y unzip make # NDK stuff

# Get SDK tools (link from https://developer.android.com/studio/index.html#downloads)
wget https://dl.google.com/android/android-sdk_r24.4.1-linux.tgz
tar xf android-sdk*-linux.tgz

# Get NDK (https://developer.android.com/ndk/downloads/index.html)
wget https://dl.google.com/android/repository/android-ndk-r16b-linux-x86_64.zip
unzip android-ndk*.zip

# Let it update itself and install some stuff
# Download every build-tools version that has ever existed
# This will save you time! Thank me later for this
cd android-sdk-linux/tools
./android update sdk --no-ui --all --filter 1,2,3,4,5,6,7,43,44,45,46,47,48,49

# If you need additional packages for your app, check available packages with:
# ./android list sdk --all

# install certain packages with:
# ./android update sdk --no-ui --all --filter 1,2,3,<...>,N
# where N is the number of the package in the list (see previous command)


# Add the directory containing executables in PATH so that they can be found
echo 'export ANDROID_HOME=$HOME/android-sdk-linux' >> ~/.bashrc
echo 'export PATH=$PATH:$ANDROID_HOME/tools:$ANDROID_HOME/platform-tools' >> ~/.bashrc

source ~/.bashrc

# Make sure you can execute 32 bit executables if this is 64 bit machine, otherwise skip this
dpkg --add-architecture i386
apt-get update
apt-get install -y libc6:i386 libstdc++6:i386 zlib1g:i386

# Add some swap space, useful if you've got less than 2G of RAM
fallocate -l 2G /swapfile 
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile

# Optionally run build system as daemon (speeds up build process)
mkdir ~/.gradle
echo 'org.gradle.daemon=true' >> ~/.gradle/gradle.properties
# See here: https://www.timroes.de/2013/09/12/speed-up-gradle/


# Build OpenALPR Android Script

#!/bin/bash

cd $SCRIPTPATH

# You should tweak this section to adapt the paths to your need
export ANDROID_HOME=$SCRIPTPATH/android-sdk-linux
export NDK_ROOT=$SCRIPTPATH/android-ndk-r16b

ANDROID_PLATFORM="android-21"

# In my case, FindJNI.cmake does not find java, so i had to manually specify these
# You could try without it and remove the cmake variable specification at the bottom of this file
JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64
JAVA_AWT_LIBRARY=$JAVA_HOME/jre/lib/amd64
JAVA_JVM_LIBRARY=$JAVA_HOME/jre/lib/amd64
JAVA_INCLUDE_PATH=$JAVA_HOME/include
JAVA_INCLUDE_PATH2=$JAVA_HOME/include/linux
JAVA_AWT_INCLUDE_PATH=$JAVA_HOME/include



####################################################################
# Prepare Tesseract and Leptonica, using rmtheis/tess-two repository
####################################################################


git clone --recursive https://github.com/rmtheis/tess-two.git tess2

cd tess2
echo "sdk.dir=$ANDROID_HOME
ndk.dir=$NDK_ROOT" > local.properties
./gradlew assemble
cd ..


####################################################################
# Download and extract OpenCV4Android
####################################################################

wget -O opencv-3.2.0-android-sdk.zip -- https://sourceforge.net/projects/opencvlibrary/files/opencv-android/3.2.0/opencv-3.2.0-android-sdk.zip/download 
unzip opencv-3.2.0-android-sdk.zip
rm opencv-3.2.0-android-sdk.zip

####################################################################
# Download and configure openalpr from jav974/openalpr forked repo
####################################################################

git clone https://github.com/kevinjpetersen/openalpr.git openalpr
mkdir openalpr/android-build

TESSERACT_SRC_DIR=$SCRIPTPATH/tess2/tess-two/jni/com_googlecode_tesseract_android/src

rm -rf openalpr/src/openalpr/ocr/tesseract
mkdir openalpr/src/openalpr/ocr/tesseract
shopt -s globstar
cd $TESSERACT_SRC_DIR

cp **/*.h $SCRIPTPATH/openalpr/src/openalpr/ocr/tesseract

cd $SCRIPTPATH

declare -a ANDROID_ABIS=("armeabi"
			 "armeabi-v7a"
			 "armeabi-v7a with NEON"
			 "arm64-v8a"
			 "mips"
			 "mips64"
			 "x86"
			 "x86_64"
			)

cd openalpr/android-build

for i in "${ANDROID_ABIS[@]}"
do
    if [ "$i" == "armeabi-v7a with NEON" ]; then abi="armeabi-v7a"; else abi="$i"; fi
    TESSERACT_LIB_DIR=$SCRIPTPATH/tess2/tess-two/libs/$abi

    if [[ "$i" == armeabi* ]];
    then
	arch="arm"
	lib="lib"
    elif [[ "$i" == arm64-v8a ]];
    then
	arch="arm64"
	lib="lib"
    elif [[ "$i" == mips ]] || [[ "$i" == x86 ]];
    then
	arch="$i"
	lib="lib"
    elif [[ "$i" == mips64 ]] || [[ "$i" == x86_64 ]];
    then
	arch="$i"
	lib="lib64"
    fi
    
    echo "
######################################
Generating project for arch $i
######################################
"
    rm -rf "$i" && mkdir "$i"
    cd "$i"
    
    cmake \
	-DANDROID_TOOLCHAIN=clang \
	-DCMAKE_TOOLCHAIN_FILE=$NDK_ROOT/build/cmake/android.toolchain.cmake \
	-DANDROID_NDK=$NDK_ROOT \
	-DCMAKE_BUILD_TYPE=Release \
	-DANDROID_PLATFORM=$ANDROID_PLATFORM \
	-DANDROID_ABI="$i" \
	-DANDROID_STL=gnustl_static \
	-DANDROID_CPP_FEATURES="rtti exceptions" \
	-DTesseract_INCLUDE_BASEAPI_DIR=$TESSERACT_SRC_DIR/api \
	-DTesseract_INCLUDE_CCSTRUCT_DIR=$TESSERACT_SRC_DIR/ccstruct \
	-DTesseract_INCLUDE_CCMAIN_DIR=$TESSERACT_SRC_DIR/ccmain \
	-DTesseract_INCLUDE_CCUTIL_DIR=$TESSERACT_SRC_DIR/ccutil \
	-DTesseract_LIB=$TESSERACT_LIB_DIR/libtess.so \
	-DLeptonica_LIB=$TESSERACT_LIB_DIR/liblept.so \
	-DOpenCV_DIR=$SCRIPTPATH/OpenCV-android-sdk/sdk/native/jni \
	-DJAVA_AWT_LIBRARY=$JAVA_AWT_LIBRARY \
	-DJAVA_JVM_LIBRARY=$JAVA_JVM_LIBRARY \
	-DJAVA_INCLUDE_PATH=$JAVA_INCLUDE_PATH \
	-DJAVA_INCLUDE_PATH2=$JAVA_INCLUDE_PATH2 \
	-DJAVA_AWT_INCLUDE_PATH=$JAVA_AWT_INCLUDE_PATH \
	-DPngt_LIB=$TESSERACT_LIB_DIR/libpngt.so \
	-DJpgt_LIB=$TESSERACT_LIB_DIR/libjpgt.so \
	-DJnigraphics_LIB=$NDK_ROOT/platforms/$ANDROID_PLATFORM/arch-$arch/usr/$lib/libjnigraphics.so \
	-DANDROID_ARM_MODE=arm \
	../../src/

    cmake --build . -- -j 8
    
    cd ..
done

echo "Everything is done! You're welcome!"

Thank you for the script. I compiled it successfully. However, I am not able to succesfully add the library to the existing Android projects? Which files and libraries has to be included in android's CMakeLists.txt? Thank you

Did you try this with latest openalpr repository?

I don't get how this is supposed to be used with Android. No .so files are built.

Mmmmh, okay in fact the build failed. After all the cmake, I get

[ 81%] Built target support
[ 81%] Built target video
make[2]: *** No rule to make target '/home/arthur/tess2/tess-two/libs/armeabi-v7a/libtess.so', needed by 'openalpr/libopenalpr.so'.  Stop.
CMakeFiles/Makefile2:584: recipe for target 'openalpr/CMakeFiles/openalpr.dir/all' failed
make[1]: *** [openalpr/CMakeFiles/openalpr.dir/all] Error 2
Makefile:149: recipe for target 'all' failed
make: *** [all] Error 2

If I try to cd into one of the android-builds/* folder and type make, I always get the same error