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adding a copy of the wiki entry for android build
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Ethan Rublee
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android/android.wiki
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156
android/android.wiki
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= Android =
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Android is awesome, and so is OpenCV, so wouldn't it be awesomer if they could work together? Well they can, and its now officially supported in opencv trunk.
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= quick ubuntu opencv static libs build =
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* install swig {{{sudo apt-get install swig}}}
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* unzip the crystax ndk r4 to your home directory http://www.crystax.net/android/ndk-r4.php
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* svn up your opencv - from https://code.ros.org/svn/opencv/trunk/opencv
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{{{
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cd opencv/android
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mkdir build
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cd build
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cmake ..
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make
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}}}
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= Prerequisites =
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* swig 1.3 - stable version in your package manager or from cygwin or from http://swig.org/
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* crystax ndk r4 - http://www.crystax.net/android/ndk-r4.php - unzip/untar to your home directory for easy cmake locating
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* android sdk latest - http://developer.android.com/sdk/index.html
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* ant build system - for compiling android apps on command line
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* (optional) eclipse android sdk adt plugin and eclipse cdt http://developer.android.com/sdk/eclipse-adt.html
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* latest code from opencv svn trunk - from https://code.ros.org/svn/opencv/trunk/opencv
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= android ndk =
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This will not work with the official release of the android ndk.
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The official android ndk does not support c++ concepts fully like RTTI, exceptions, and most of the stl.
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Make sure you use the modified android ndk from crystax available at http://www.crystax.net/android/ndk-r4.php
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The android ndk, now referred to as the ndk, is the gcc toolchain for android, and is what creates the shared
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libraries for android that are loadable by android apps through a the Java Native Interface(JNI)
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Recommended install of the ndk is to unzip it to your home directory
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For example this is what mine looks like:
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{{{
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erublee@bde:~/android-ndk-r4-crystax$ ls
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build docs GNUmakefile ndk-build ndk-gdb README.TXT samples sources
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}}}
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= Android SDK =
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Please read the very well documented android sdk getting started instructions - http://developer.android.com/sdk/index.html and at least build and install a hello world app on your Android phone.
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== Android SDK tips ==
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I always add the android sdk tools directory to my path so i can run the adb from any where.
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On ubuntu, add the following to your {{{~/.bashrc}}}
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{{{
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export PATH=~/android-sdk-linux_x86/tools:$PATH
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}}}
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Install ant so that you can build from command line.
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Make sure your udev permissions are set for usb debug and that the phone itself is set to allow debugging
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http://developer.android.com/guide/developing/device.html#setting-up
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Nexus one users on ubuntu lucid should have the following udev file:
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{{{
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/etc/udev/rules.d/51-android.rules
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SUBSYSTEM=="usb", SYSFS{idVendor}=="18d1", MODE="0666"
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}}}
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see the following blog post on why http://alan.lamielle.net/2010/01/22/nexus-one-usb-in-ubuntu-9-10
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= How and What =
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The android port involves high jacking the existing cmake build files and replacing the define_opencv_module with android specific build commands.
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In particular the cmake based build creates android ndk build files and calls the android ndk to build opencv.
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== OpenCV static libs ==
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The main cmake build of opencv generates a static lib for each module and some of the 3rdparty libraries. These can then be linked against in your own android projects.
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the cmake build will also generate an android-opencv.mk file in the build folder. Include this file in your Android.mk files to link against the static libs.
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this would go in your Android.mk file. See the docs in the ndk for an explanation of LOCAL_LDLIBS and LOCAL_C_INCLUDES.
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{{{
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#define OPENCV_INCLUDES and OPENCV_LIBS
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include $(PATH_TO_OPENCV_ANDROID_BUILD)/android-opencv.mk
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LOCAL_LDLIBS += $(OPENCV_LIBS)
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LOCAL_C_INCLUDES += $(OPENCV_INCLUDES)
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}}}
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== OpenCV shared library ==
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There is an attempt at a library that is more generally useful for android that could also be linked against in your on projects. This project is under
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opencv/android/android-jni
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This uses swig to expose some functions to java. Also it implements a live camera preview interface, so that you can have access to the Android camera for live vision apps.
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== Apps ==
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A few sample apps that use the library are under opencv/android/apps
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* CVCamera is a complete example that uses the opencv static libs and the android-jni project
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* Calibration is a stand alone camera calibration app for your Android that is pure java and links against the android-jni project - use this app to make a camera.yml calibration file in your sdcard's home directory
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* more to come ...
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= steps =
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=== Static libs ===
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{{{
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cd opencv/android
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mkdir build
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cd build
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cmake ..
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make
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}}}
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this may take a while
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=== android-jni ===
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After the static libs are built, run make in the android-jni folder
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{{{
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cd opencv/android/android-jni
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make
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}}}
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That creates the swig wrappers and compiles the shared library.
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now run the ant based java build
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{{{
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sh ./project_create.sh
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ant debug
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}}}
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Now you're ready to use it in a sample
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=== CVCamera ===
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{{{
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cd opencv/android/apps/CVCamera
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sh build.sh
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}}}
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That builds the swig wrappers and shared library.
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Build the android apk ( the thing that gets installed on the phone )
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{{{
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sh project_create.sh
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ant debug
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}}}
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Now if everything worked, try to install it. Connect your device and run the following
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{{{
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ant install
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}}}
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Run it, press menu to see options - right now it can draw fast, star, and surf feature points on the live preview image.
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=== Calibration ===
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{{{
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sh project_create.sh
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ant debug
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ant install
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}}}
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To run the app, make sure that the sdcard is not mounted on your computer and point the phone at a calibration pattern and snap away. When you have taken enough chessboards to satisfy yourself
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press the save button to have the camera calibarted. The calibration will be saved to /sdcard/opencv/calibration.yml
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Also see this app for how to make a slightly nicer camera ui than CVCamera.
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=== Troubles ===
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try to edit the local.env.mk file's that get created in CVCamera and android-jni to reflect your system.
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Also using cmake-gui or ccmake are good options to set up where your ndk directory are.
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Send questions/comments to Ethan Rublee ethan.rublee@gmail.com
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= Programming your own apps =
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Try to look at the samples - like CVCamera, for how to do this. A tutorial may be forth coming.
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