@ -141,7 +141,7 @@ Open OpenCV library and samples in Eclipse
#. Start the *Eclipse* and choose your workspace location.
I recommend to start familiarising yourself with OpenCV for Android from a new clean workspace. So I have chosen my OpenCV package directory for the new workspace:
I recommend to start familiarizing yourself with OpenCV for Android from a new clean workspace. So I have chosen my OpenCV package directory for the new workspace:
..image:: images/eclipse_1_choose_workspace.png
:alt:Choosing C:\Work\android-opencv\ as workspace location
@ -280,3 +280,8 @@ If you already have an Android application, you can add a reference to OpenCV an
Do the right mouse click on your app in Package Explorer, go to **Properties > Android > Library > Add**
and choose the OpenCV library project.
Whats next?
===========
Read the :ref:`Android_Binary_Package_with_NDK` tutorial to learn how add native OpenCV code to your Android project.
This tutorial describes a simple way to build Android application which uses OpenCV from the native (C++) level.
This tutorial describes a fast way how to create and build Android applications containing OpenCV code written in C++ with OpenCV binary package.
This is impotant when you have some functionality which is written in C++ and uses OpenCV, and you want to use it in your Android application,
but do not want to rewrite the C++ code to Java (e.g. if the speed is critical for this part of the code).
This is important when you already have some computer vision functionality which is written in C++ and uses OpenCV, and you want to use it in your Android application,
but do not want to rewrite the C++ code to Java.
In this case the only way is to use JNI mechanism.
It means, that you should add a class with native methods wrapping your C++ functionality into the Java part of your Android application.
In this case the only way is to use JNI.
It means, that into the Java code of your Android application should be added a Java class with native methods,
which will be wrappers for your C++ functionality.
This tutorial describes a way how to use OpenCV binary package to compile Android applications, which contains C++ native code using OpenCV.
Note that before using this tutorial you should fulfill all the operations,
described in the tutorial :ref:`Android_Binary_Package` .
Please note that before starting this tutorial you should fulfill all the steps, described in the tutorial :ref:`Android_Binary_Package`.
The tutorial was tested using Ubuntu 10.04 operating systems (Windows 7 SP1 coming soon).
Nevertheless, it should also work on Mac OS X. If you encounter errors after following the steps described here, feel free to contact us via *android-opencv* discussion group https://groups.google.com/group/android-opencv/ and we will try to help you.
Setup NDK
==============================================
To compile C++ code for using in Android applications you need Android NDK.
Prerequisites: Setup NDK
========================
You can get the latest version of Android NDK as an archive from the page http://developer.android.com/sdk/ndk/index.html .
To compile C++ code for Android platform you need Android NDK.
To install Android NDK just extract the archive to some folder on your computer.
You can get the latest version of NDK from the page http://developer.android.com/sdk/ndk/index.html .
To install Android NDK just extract the archive to some folder on your computer. Here is installation instructions on the NDK home page: http://developer.android.com/sdk/ndk/index.html#installing
Android NDK Documentation
==============================================
..note:: Before start you can read official Android NDK documentation which is in the Android NDK archive, in the folder :file:`docs/`.
Before start you can read official Android NDK documentation which is in the Android NDK archive, in the folder **docs/**.
The main article about using Android NDK build system you can read in the file :file:`ANDROID-MK.html`.
The main article about using Android NDK build system you can read in the file **ANDROID-MK.html**.
Also some additional useful information you can read in the files
:file:`APPLICATION-MK.html`, :file:`NDK-BUILD.html`, and in the files :file:`CPU-ARM-NEON.html`, :file:`CPLUSPLUS-SUPPORT.html`, :file:`PREBUILTS.html`.
Also some additional useful information you can read in the files
**APPLICATION-MK.html**, **NDK-BUILD.html**, and in the files **CPU-ARM-NEON.html**, **CPLUSPLUS-SUPPORT.html**, **PREBUILTS.html**.
Theory: Android application structure
=====================================
Android application source code structure
==========================================
Usually code of an Android application has the following structure:
Usually source code of an Android application has the following structure:
+ :file:`root folder of the project/`
+ root folder of the project/
- :file:`jni/`
- jni/
- :file:`libs/`
- res/
- :file:`res/`
- src/
- :file:`src/`
- AndroidManifest.xml
- :file:`AndroidManifest.xml`
- default.properties
- :file:`default.properties`
- ... other files ...
- :file:`... other files ...`
where
+ the folder **src** contains the Java code of the application,
+ the :file:`src` folder contains the Java code of the application,
+ the folder **res** contains resources of the application (images, xml files describing the application layout, etc),
+ the :file:`res` folder contains resources of the application (images, xml files describing UI layout , etc),
+ and the folder **jni** contains C/C++ application source code and simple scripts **Android.mk** and **Application.mk**.
+ the :file:`libs` folder will contain native libraries after successful build,
+ and the :file:`jni` folder contains C/C++ application source code and NDK build scripts :file:`Android.mk` and :file:`Application.mk`.
These scripts control the C++ build process (they are written in Makefile language).
Also the root folder should contain the following files
* the :file:`AndroidManifest.xml` file presents essential information about the application to the Android system
(name of the Application, name of the main application's Java package, components of the application, required permissions, etc)
It can be created using Eclipse wizard or :file:`android` tool from Android SDK
* the file **AndroidManifest.xml** presents essential information about the application to the Android system
(name of the Application, name of the main application's Java package, components of the application, etc)
--- it can be created using Eclipse wizard, android tool from SDK, or manually
* the :file:`default.properties` is a text file containing information about target Android platform and other build details.
This file is generated by Eclipse or can be created with :file:`android` tool from Android SDK
* the text file **default.properties** contains information about Android target platform and some other details.
..note:: Both files (AndroidManifest.xml and default.properties) are required to compile the C++ part of the application (the Android build system uses information from these files). If the files don't exist, compile the Java part of the project before the C++ part of the project.
The file is generated by Eclipse or console ant application.
Theory: How to build Android application having C++ native part (from command line)
**Attention**: Both files (AndroidManifest.xml and default.properties) are required to compile the C++ part of the application source code (the Android build system uses information from these files). If the files don't exist, compile the Java part of the project before the C++ part of the project.
Here is the standard way to compile C++ part of an Android application:
#. Open console and go to the root folder of Android application
How to build Android application which have C++ native part (from console)
Here is the standard way to compile C++ part of an Android application:
cd <root folder of the project>/
..note:: Alternatively you can go to the folder :file:`jni` of Android project but samples from OpenCV binary package are configured for building from project root level (because of relative path to OpenCV library).
#. Open console and go to the folder jni of the application project.
#. Run the following command
..code-block:: bash
+ *UNIX*
..code-block:: bash
<path_where_NDK_is_placed>/ndk-build
<path_where_NDK_is_placed>/ndk-build
After executing this command the C++ part of the source code is compiled.
+ *Cygwin*
After that the Java part of the application can be recompiled (using either Eclipse, or ant build tool, or scripts calling ant commands, etc), and then the built application can be installed on a device.
..code-block:: bash
Note that some parameters can be set for the script ndk-build.
export NDK_USE_CYGPATH=1
<path_where_NDK_is_placed>/ndk-build
**Example 1**: Verbose compilation
..code-block:: bash
#. After executing this command the C++ part of the source code is compiled.
After that the Java part of the application can be (re)compiled (using either *Eclipse* or *ant* build tool).
..note:: Some parameters can be set for the :file:`ndk-build`:
**Example 1**: Verbose compilation
..code-block:: bash
<path_where_NDK_is_placed>/ndk-build V=1
**Example 2**: Rebuild all
**Example 2**: Rebuild all
..code-block:: bash
..code-block:: bash
<path_where_NDK_is_placed>/ndk-build -B
The tutorials 3 and 4 in OpenCV package may be compiled by this way.
.._Android_NDK_integration_with_Eclipse:
How to build Android application which have C++ native part (from Eclipse)
There are several possible ways to integrate compilation of C++ code by Android NDK into Eclipse compilation process. We recommend the approach taken from this site: http://mobilepearls.com/labs/ndk-builder-in-eclipse/
..important:: This instructions should be applied for each Android project in *Eclipse* workspace, which contains native C++ code.
Below is an adapted version of this guide:
#. Navigate to *Package Explorer* window and expand your project having JNI resources.
If you can not see :file:`libs` folder under this project then you need to create it manually.
#. Right click on your project in *Package Explorer* window and select *Properties*.
#. In the *Properties* dialog select *Builders* menu and press the *New...* button:
..image:: images/eclipse_builders.png
:alt:Configure builders
:align:center
#. In the resulting dialog select the *Program* type and press the *OK* button:
..image:: images/eclipse_builder_types.png
:alt:Choose builder type
:align:center
#. In the *Main* tab fill the following fields:
* *Name* - any name for your builder. ("Tutorial 2.1 Builder" in my case.)
..note:: This name has to be unique for each project in your workspace.
* *Location* - path to :file:`ndk-build` tool.
+ *UNIX*
Just put full path to :file:`ndk-build` into this filed. Also you can add some options to the *Arguments* fied, for example **-B** option.
+ *Cygwin*
- Instead of path to the :file:`ndk-build` tool you need to put full path to *cygwin*:file:`bash.exe` location. E.g: :file:`C:\\cygwin\\bin\\bash.exe`.
- Put full path to :file:`ndk-build` into the *Arguments* field E.g. :file:`C:\\Android\\android-ndk-r6\\ndk-build`.
- Go to the *Environment* tab and define 2 environment variables:
* **PATH** - full path to the *cygwin* tools. E.g. :file:`C:\\cygwin\\bin`
* **NDK_USE_CYGPATH** - set to 1
There is a simple way to integrate compilation of C++ code by Android NDK into Eclipse compilation process.
..image:: images/eclipse_windows_environment.png
:alt:Define environment variables
:align:center
To use it follow instructions from this site: http://mobilepearls.com/labs/ndk-builder-in-eclipse/
* *Working Directory* - put path to your project into this field. Instead of hardcoding full path you can click *Browse Workspace..." button and select your project.
**Important:** This instructions should be applied for each Android project in Eclipse workspace, which contains native C++ code.
Note that in the instructions the folder "lib" is shown on pictures, whereas the name of the folder is "libs" indeed (if the folder "libs" is absent in your project, compile the Java part of your project or just create it).
#. Go to the *Refresh* tab and select both *"Refresh resources upon completion"* and *"Recursively include sub-folders"*.
Also note that if you have followed this instructions for new project in the workspace, sometimes you will have to change the name of the builder (as example, you can give it name "NDK Builder1" instead of "NDK builder", etc)
Next click the *"Specific resources"* option and click the *"Specify resources..."* button:
The tutorials 3 and 4 in OpenCV package may be compiled by this way.
#. Finally press *OK* in the builder configuration and project properties dialogs. If you have automatic build turned on then console showing build log should appear:
..image:: images/eclipse_NDK_build_success.png
:alt:Select resources to build
:align:center
Theory: The structure of Android.mk and Application.mk scripts
The script :file:`Android.mk` usually have the following structure:
..code-block:: make
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := <module_name>
LOCAL_SRC_FILES := <list of .c and .cpp project files>
<some variable name> := <some variable value>
...
<some variable name> := <some variable value>
include $(BUILD_SHARED_LIBRARY)
This is the minimal file Android.mk, which builds a C++ source code of an Android application. Note that the first two lines and the last line are mandatory for any Android.mk.
This is the minimal file Android.mk, which builds a C++ source code of an Android application. Note that the first two lines and the last line are mandatory for any :file:`Android.mk`.
Usually the file Application.mk is optional, but sometimes, when STL or exceptions are used in C++, it also should be written. Example of the file Application.mk:
Usually the file :file:`Application.mk` is optional, but in case of project using OpenCV, when STL and exceptions are used in C++, it also should be written. Example of the file :file:`Application.mk`:
..code-block:: make
@ -167,53 +258,93 @@ Usually the file Application.mk is optional, but sometimes, when STL or exceptio
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a
How to build an Android application, which uses OpenCV
To build your own Android application, which uses OpenCV from native part, the following steps should be done:
1. The archive with OpenCV binary package should be downloaded and extracted to some folder (as example, into the home folder)
#. The archive with OpenCV binary package should be downloaded and extracted to some folder (as example, into the home folder)
#. We recommend to use an environment variable to specify the location of OpenCV package. Full or relative path hardcoded in :file:`jni/Android.mk` will also work.
2. The environment variable OPENCV_PACKAGE_DIR should be defined.
So, the environment variable **OPENCV_PACKAGE_DIR** should be defined.
The value of the variable should points to the folder, where the OpenCV package has been extracted.
As an example, you can add add the following line into the hidden file .bashrc placed in your home folder:
As an example, on *UNIX* you can add add the following line into the hidden file :file:`.bashrc` placed in your home folder:
..code-block:: bash
export OPENCV_PACKAGE_DIR = <path to the extracted OpenCV package>
Then reboot your computer.
Then relogin (or better reboot your computer).
**Attention**: without rebooting (or logout) this change won't work.
..attention:: without rebooting (or logout) this change might not work.
If you are a *Windows* user, then navigate to:
* *Windows 7 / Windows Vista*
3. The file jni/Android.mk should be written for the current application using the common rules for the file.
My Computer (Right Click on Icon) > Properties (Link) > Advanced System Settings (Link) > Advanced (Tab) > Environment Variables (Button) > System variables (Section)
* *Windows XP*
My Computer (Right Click on Icon) > Properties (Link) > Advanced (Tab) > Environment Variables (Button) > System variables (Section)
Create new variable **OPENCV_PACKAGE_DIR** and similarly to *UNIX* relogin or reboot.
If you are setting NDK builder as described above in :ref:`Android_NDK_integration_with_Eclipse`, then you can define this variable in builder settings. It can be done on third *Environment* tab of the builder configuration window (we have already added some variables to this tab on *Windows* but skipped it for other platforms).
# The file :file:`jni/Android.mk` should be written for the current application using the common rules for the file.
For detailed information see the Android NDK documentation from the Android NDK archive, in the file
include $(OPENCV_PACKAGE_DIR)/share/OpenCV/OpenCV.mk
should be inserted into the jni/Android.mk file right after the line
should be inserted into the :file:`jni/Android.mk` file right after the line
..code-block:: make
include $(CLEAR_VARS)
(check the path to the included file)
5. Also the line
..code-block:: make
..note:: If your application utilize both native (C++) OpenCV and its Java API you need to put the following line before including :file:`OpenCV.mk` to avoid conflict between C++ and Java builders:
LOCAL_ARM_NEON := true
..code-block:: make
is recommended to be added to the jni/Android.mk file, if the application should be run on Android devices with ARM NEON support.
OPENCV_CAMERA_MODULES:=off
6. The file Application.mk should exist and should contain lines
#. The file :file:`Application.mk` should exist and should contain lines
..code-block:: make
@ -226,13 +357,13 @@ To build your own Android application, which uses OpenCV from native part, the f
APP_ABI := armeabi-v7a
is recommended to run the application on modern ARMs
is recommended for the applications targeting modern ARMs
7. To build the C++ code the Android NDK script **ndk-build** should be run in the root directory of application.
#. To build the C++ code the Android NDK script :file:`ndk-build` should be run in the root directory of application.
Then the C++ source code using OpenCV will be built by Android NDK build system.
After that the Java part of the application can be rebuild and the application can be installed on an Android device.
Note that this step requires calling the ndk-build script from the console; instead of this step you can use integration of Android NDK into Eclipse
Note that this step requires calling the :file:`ndk-build` script from the console; instead of this step you can use integration of Android NDK into Eclipse
as stated above in the section :ref:`Android_NDK_integration_with_Eclipse` .
@ -243,7 +374,7 @@ Note that you can install additional C++ plugins in Eclipse:
#. Open Help / Install New Software. This shows the “Install” dialog.
#. In the “Work with” dropdown list choose "Helios - http://download.eclipse.org/releases/helios" and wait while the list of
#. In the “Work with” drop-down list choose "Helios - http://download.eclipse.org/releases/helios" and wait while the list of
available software is loaded.
#. From the list of available software select “Programming Languages” / “C/C++ Development Tools 7.0.1”.
Andrey Kamaev
14 years ago
