Introduction to OpenCV for Android devices

Transcription

1 AT : Selected Topic: Cloud Robotics July 12, 2012 Asian Institute of Technology Computer Science and Information Management Handout: Introduction to OpenCV for Android devices Instructor: Karn Yongsiriwit Introduction to OpenCV for Android devices Instructions: In this tutorial, we will get started with the OpenCV for Android development tools. After that, we will create a simple HelloWorld application running on your Android device. Therefore, we will get some Android applications using OpenCV up and running. A. What we need before we start the tutorial 1. Ubuntu desktop running on your computer, version is recommended 2. Android device with Android version 2.2 or above, including USB cable 3. Download all needed files for this tutorial from: B. Install Oracle Java SDK To install Oracle Java SDK, simply run the following commands: $ chmod u+x jdk-6u33-linux-i586.bin $./jdk-6u33-linux-i586.bin $ sudo mv jdk1.6.0 f33/ /usr/lib/jvm/ $ sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk /bin/java" 1 Note: OpenJDK is not usable for Android development because Android SDK supports only Oracle SDK You can check whether your java is installed properly by running the following command to see the result: $ java -version java version " " Java(TM) SE Runtime Environment (build b03) Java HotSpot(TM) Server VM (build 20.8-b03, mixed mode) Credit: 1

2 C. Install Eclipse IDE Eclipse IDE is our main tool for this tutorial. Simply extract eclipse tar file to your home directory using the command bellow. In my case, the extracted eclipse directory will be /home/karn/eclipse $ tar -C ~ -zxvf eclipse-sdk-4.2-linux-gtk.tar.gz D. Install ADT Plugin 1. Start Eclipse, then select Help > Install New Software Click Add, in the top-right corner. 3. In the Add Repository dialog, enter ADT Plugin for the Name and the following URL for the Location: or if you encounter some problems with the first one. 4. In the Available Software dialog, select the checkbox next to Developer Tools and click Next. Follow the instruction until the installation completes, restart Eclipse. E. Configure Android SDK 1. Extract downloaded android-sdks.tar.gz to your home directory using the following command. In my case, the extracted Android SDK directory will be /home/karn/android-sdks $ tar -C ~ -zxvf android-sdks.tar.gz 2. When Eclipse is restarted after the installation of ADT Plugin, you will be asked to configure Android SDK, I recommend you to select Use existing SDKs and browse your Android SDK directory. For example, my Android SDK directory is /home/karn/android-sdks 3. The given Andorid SDK contains only version 2.2, 2.3.3, 3.0, 3.2 and 4.1. If your device is using different version, you may install it manually in Eclipse by selecting Window > Android SDK Manager Note: You may check the version of Android on your device by selecting Settings > About device > Firmware version. For example, my Android version is F. Turn on USB Debugging on your Android device On the device, go to Settings > Applications > Development and enable USB debugging (on an Android 4.0 device, the setting is located in Settings > Developer options) 2

3 G. Set up your system to detect your Android device 1. create /etc/udev/rules.d/51-android.rules file: $ sudo gedit /etc/udev/rules.d/51-android.rules 2. Add the following line into the file: SUBSYSTEM=="usb", ATTRidVendor=="<ID>", MODE="0666", GROUP="plugdev" Where <ID> is replaced by your USB vendor ID. For instance, Samsung is 04e8, Acer is 0502 and HTC is 0bb4. For example, my device is Samsung so it will be: SUBSYSTEM=="usb", ATTRidVendor=="04e8", MODE="0666", GROUP="plugdev" For more information regarding the USB vendor ID, please visit: H1. Create and run Android application on your device 1. In Eclipse, select File > New > Project. The resulting dialog should have a directory labelled Android. 2. Open the Android directory, select Android Project and click Next. 3. Enter a project name (such as MyFirstApp ). 4. Select a build target depending on your Android device. This is the platform version against which you will compile your application. Click Next and then Next. 5. In Create Activity, select BlankActivity and then click Next, then click Finish. 6. Right-click on your project in the left panel, select Run As > Run Configurations Select Target tab, then select Always prompt to pick device, click Apply and then Close. 8. Run your project by selecting Run > Run. 9. Make sure that your Android device is connected via USB and the status is online as shown in the device status, then click OK. 10. Your application will be installed on your device and executed. If you see Hello world! in middle of your screen, that means it works!! Credit: 3

4 H2. Create a simple user interface 1. Open the activity main.xml file from the res/layout/ directory, select activity main.xml tab. 2. Change the layout to LinearLayout which is a view group that lays out child views in either a vertical or horizontal orientation, add a text field and a button by replacing the existing code with the following code: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android=" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal"> <EditText android:id="@+id/edit_message" android:layout_weight="1" android:layout_width="0dp" android:layout_height="wrap_content" android:hint="@string/edit_message" /> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/button_send" /> </LinearLayout> 3. Add String resources by opening res/values/strings.xml, then add the code bellow: <string name="edit_message">enter a message</string> <string name="button_send">send</string> 4. Run this application on your device, you will see one text field and one button on your screen. Credit: H3. Start another activity 1. Open res/layout/main.xml, modify the button element as bellow: <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/button_send" android:onclick="sendmessage" /> 2. Open src/<package-name>/mainactivity.java, then add one line as the first line of the class as shown bellow. Note that <package-name> need to be change to your package name. public class MyFirstActivity extends Activity { public final static String EXTRA_MESSAGE = "<package-name>.message";... } For instance, mine is: public final static String EXTRA_MESSAGE = "com.example.myfirstandroidapp.message"; 4

5 Therefore, add the following code inside the class: /** Called when the user selects the Send button */ public void sendmessage(view view) { // Do something in response to button Intent intent = new Intent(this, DisplayMessageActivity.class); EditText edittext = (EditText) findviewbyid(r.id.edit_message); String message = edittext.gettext().tostring(); intent.putextra(extra_message, message); startactivity(intent); } After that, select Source > Organize Imports after finish modification 3. Create new activity by right-clicking the package name under the src/ directory and select New > Class. Enter DisplayMessageActivity for the name and android.app.activity for the superclass. After that add oncreate() callback method into the class as public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); // Get the message from the intent Intent intent = getintent(); String message = intent.getstringextra(mainactivity.extra_message); // Create the text view TextView textview = new TextView(this); textview.settextsize(40); textview.settext(message); } setcontentview(textview); 4. Declare new activity in AndroidManifest.xml by adding new activity element inside application element as follow. Note that <package-name> need to be change to your package name. <application... > <activity android:name="<package-name>.displaymessageactivity" />... </application> 5. Run and test your application on your device. Now you can go from one activity to another by simply clicking on send button. Credit: I. Setup and run OpenCV application on Android device 1. Extract downloaded OpenCV android-sdk.zip to your home directory using the following command. In my case, it will be extracted to /home/karn/opencv android-sdk $ unzip OpenCV android-sdk.zip -d ~ 5

6 2. Let start with importing library into our workspace. In Eclipse, select File > Import > General > Existing projects into Workspace, then click Next. 3. Check on Select root directory, browse for OpenCV android-sdk/sdk/java in your home directory, then click OK. 4. Check on OpenCV Library in Projects list, then click Finish. 5. Right-click on OpenCV Library project and select Properties. 6. Select Android on the left panel, and check Android 3.0 for Project Build Target, then click OK. 7. Now, we can import tutorials given by this SDK by selecting File > Import > General > Existing projects into Workspace, then click Next. 8. Check on Select root directory, browse for OpenCV android-sdk/samples in your home directory, then click OK. 9. Make sure all projects in Projects list are checked, then click Finish. 10. At this point, you will be able to run applications using Java OpenCV API. Therefore, you can run and test Java API usage projects as follows: (a) Tutorial 0 - Android Camera: this example is a skeleton application for all the other samples. It does not use OpenCV at all, but gives you an example Android application working with camera. (b) Tutorial 1 - Add OpenCV: shows the simplest way to add OpenCV call to the Android application. (c) Tutorial 2 - Use OpenCV Camera: this sample does exactly the same as the previous one, but uses OpenCVs native camera for video capturing. (d) Sample - 15-puzzle: a simple game can be implemented with just a few calls to OpenCV. (e) Sample - color-blob-detection: trivial implementation of color blob tracker. Work with touch interface and contours is demonstrated. (f) Sample - image-manipulations: this example demonstrates how OpenCV can be used as an image processing and manipulation library. Note: When you first running application using OpenCV on your Android device, you will be asked to install OpenCV Manager and OpenCV library from Google Play. Credit: J. Using C++ OpenCV code with Android binary package 1. We will install and use CDT (C/C++ Development Tools) plugin in Eclipse together with Android Native Development Kit (NDK) in order to use C++ OpenCV code in Android application. Firstly, we can start from installing CDT plugin. in Eclipse, select Help > Install New Software Click Add, in the top-right corner. 3. In the Add Repository dialog, enter CDT for the Name and the following URL for the Location: 4. In the Available Software dialog, select the checkbox next to CDT Main Features and click Next. Follow the instruction until the installation completes, restart Eclipse. 6

7 5. After restart, switch Eclipse perspective to C/C++ by selecting Window > Open Perspective > Other... then select C/C++ and click OK. 6. Therefore, install NDK by simply extract android-ndk-r8-linux-x86.tar.bz2 into your home directory using the command bellow. In my case, the extracted NDK folder will be /home/karn/androidndk-r8 $ tar -C ~ -jxvf android-ndk-r8-linux-x86.tar.bz2 7. At this point, you will be able to run applications using both C++ and Java OpenCV API. The application using native C++ OpenCV API are as follows: (a) Tutorial 3 - Add Native OpenCV: this example demonstrates how you can use OpenCV in the native part of your application through JNI (Java Native Interface). (b) Tutorial 4 - Mix Java + Native OpenCV: shows how to use both C++ and Java OpenCV API in a single application. (c) Sample - face-detection: the simplest implementation of the face detection functionality on Android. It supports 2 modes of execution: available by default Java wrapper for the cascade classifier, and manually crafted JNI call to a native class which supports tracking. 8. However, each of those projects need to be configure and modify as following steps: (a) Modify jni/android.mk: Change one line from: include../../sdk/native/jni/opencv.mk to include \${HOME}/OpenCV android-sdk/sdk/native/jni/OpenCV.mk (b) Right-click on the project and select Properties. (c) Select C/C++ Build, choose Builder Settings tab, then change Build command: to \${HOME}/android-ndk-r8/ndk-build (d) Select C/C++ General > Paths and Symbol on the left panel, then select include tab, choose GNU C++ language, remove existing include directories and add the followings: ${HOME}/android-ndk-r8/platforms/android-9/arch-arm/usr/include ${HOME}/android-ndk-r8/sources/cxx-stl/stlport/stlport ${HOME}/OpenCV android-sdk/sdk/native/jni/include (e) Right-click on the project, then select Clean Project. (f) Now we can build the C++ source code inside the project by right-clicking on the project, then select Build Project. Make sure there is no error. 9. you should be able to run all given tutorials. Enjoy!! Credit: package_using_with_ndk.html Note: for more details on the installation or how to use OpenCV API in details, please have a look at doc/opencv tutorials.pdf on your OpenCV android-sdk directory 7

8 References Java on Ubuntu Using Hardware Devices for Android developers html Building Your First App for Android developers firstapp/index.html OpenCV4Android Samples html Using C++ OpenCV code with Android binary package introduction/android_binary_package/android_binary_package_using_with_ndk.html 8