eclipse开发opencv官方教程

素颜马尾好姑娘i 2022-07-21 01:17 114阅读 0赞

# Introduction to Java Development #

Last updated: 12 February, 2013.

As of OpenCV 2.4.4, OpenCV supports desktop Java development using nearly the same interface as for Android development. This guide will help you to create your first Java (or Scala) application using OpenCV. We will use either [Eclipse][], [Apache Ant][] or the [Simple Build Tool (SBT)][Simple Build Tool _SBT] to build the application.

For further reading after this guide, look at the [*Introduction into Android Development*][Introduction into Android Development] tutorials.

# What we’ll do in this guide #

In this guide, we will:

*  Get OpenCV with desktop Java support
 *  Create an Ant, Eclipse or SBT project
 *  Write a simple OpenCV application in Java or Scala

The same process was used to create the samples in the samples/java folder of the OpenCV repository, so consult those files if you get lost.

# Get OpenCV with desktop Java support #

Starting from version 2.4.4 OpenCV includes desktop Java bindings. The most simple way to get it is downloading the appropriate package of **version 2.4.4 or higher** from the [OpenCV SourceForge repository][].

Note

Windows users can find the prebuilt files needed for Java development in the opencv/build/java/ folder inside the package. For other OSes it’s required to build OpenCV from sources.

Another option to get OpenCV sources is to clone [OpenCV git repository][]. In order to build OpenCV with Java bindings you need JDK (we recommend [Oracle/Sun JDK 6 or 7][Oracle_Sun JDK 6 or 7]), [Apache Ant][] and Python v2.6 or higher to be installed.

## Build OpenCV ##

Let’s build OpenCV:

>     git clone git://github.com/Itseez/opencv.git
>     cd opencv
>     git checkout 2.4
>     mkdir build
>     cd build

Generate a Makefile or a MS Visual Studio\* solution, or whatever you use for building executables in your system:

>     cmake -DBUILD_SHARED_LIBS=OFF ..

>     cmake -DBUILD_SHARED_LIBS=OFF -G "Visual Studio 10" ..

Note

When OpenCV is built as a set of **static** libraries (\-DBUILD\_SHARED\_LIBS=OFF option) the Java bindings dynamic library is all-sufficient, i.e. doesn’t depend on other OpenCV libs, but includes all the OpenCV code inside.

Examine the output of CMake and ensure java is one of the modules “To be built”. If not, it’s likely you’re missing a dependency. You should troubleshoot by looking through the CMake output for any Java-related tools that aren’t found and installing them.

> ![CMake output][]

Now start the build:

>     make -j8

>     msbuild /m OpenCV.sln /t:Build /p:Configuration=Release /v:m

Besides all this will create a jar containing the Java interface (bin/opencv\_2.4.4.jar) and a native dynamic library containing Java bindings and all the OpenCV stuff (bin/Release/opencv\_java244.dllor bin/libopencv\_java244.so respectively). We’ll use these files later.

# Create a simple Java sample and an Ant build file for it #

Note

The described sample is provided with OpenCV library in the opencv/samples/java/ant folder.

* Create a folder where you’ll develop this sample application.
 * In this folder create an XML file with the following content using any text editor:
 
 > <table style="margin-left:0.5em"> 
 > <tbody> 
 > <tr> 
 > <td style="padding:0px 0.5em"> 
 > <div style="min-width:1em; text-align:right"> 
 > <pre style="overflow-x:auto; overflow-y:hidden; padding:5px 0px; color:rgb(170,170,170); line-height:15.6px; border:0px; background-color:transparent"> 1
 > 2
 > 3
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 > 5
 > 6
 > 7
 > 8
 > 9
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 > 11
 > 12
 > 13
 > 14
 > 15
 > 16
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 > 18
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 > 20
 > 21
 > 22
 > 23
 > 24
 > 25
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 > 49</pre> 
 > </div> </td> 
 > <td style="padding:0px 0.5em"> 
 > <div style="background:rgb(238,255,204)"> 
 > <pre style="overflow-x:auto; overflow-y:hidden; padding:5px; color:rgb(51,51,51); line-height:15.6px; border-top-width:1px; border-bottom-width:1px; border-style:solid none; border-top-color:rgb(170,204,238); border-bottom-color:rgb(170,204,238); background-color:rgb(224,245,255)">&lt;project name="SimpleSample" basedir="." default="rebuild-run"&gt;
 > 
 > &lt;property name="src.dir" value="src"/&gt;
 > 
 > &lt;property name="lib.dir" value="${ocvJarDir}"/&gt;
 > &lt;path id="classpath"&gt;
 > &lt;fileset dir="${lib.dir}" includes="**/*.jar"/&gt;
 > &lt;/path&gt;
 > 
 > &lt;property name="build.dir" value="build"/&gt;
 > &lt;property name="classes.dir" value="${build.dir}/classes"/&gt;
 > &lt;property name="jar.dir" value="${build.dir}/jar"/&gt;
 > 
 > &lt;property name="main-class" value="${ant.project.name}"/&gt;
 > 
 > 
 > &lt;target name="clean"&gt;
 > &lt;delete dir="${build.dir}"/&gt;
 > &lt;/target&gt;
 > 
 > &lt;target name="compile"&gt;
 > &lt;mkdir dir="${classes.dir}"/&gt;
 > &lt;javac srcdir="${src.dir}" destdir="${classes.dir}" classpathref="classpath"/&gt;
 > &lt;/target&gt;
 > 
 > &lt;target name="jar" depends="compile"&gt;
 > &lt;mkdir dir="${jar.dir}"/&gt;
 > &lt;jar destfile="${jar.dir}/${ant.project.name}.jar" basedir="${classes.dir}"&gt;
 > &lt;manifest&gt;
 > &lt;attribute name="Main-Class" value="${main-class}"/&gt;
 > &lt;/manifest&gt;
 > &lt;/jar&gt;
 > &lt;/target&gt;
 > 
 > &lt;target name="run" depends="jar"&gt;
 > &lt;java fork="true" classname="${main-class}"&gt;
 > &lt;sysproperty key="java.library.path" path="${ocvLibDir}"/&gt;
 > &lt;classpath&gt;
 > &lt;path refid="classpath"/&gt;
 > &lt;path location="${jar.dir}/${ant.project.name}.jar"/&gt;
 > &lt;/classpath&gt;
 > &lt;/java&gt;
 > &lt;/target&gt;
 > 
 > &lt;target name="rebuild" depends="clean,jar"/&gt;
 > 
 > &lt;target name="rebuild-run" depends="clean,run"/&gt;
 > 
 > &lt;/project&gt;
 > </pre> 
 > </div> </td> 
 > </tr> 
 > </tbody> 
 > </table>
 > 
 > Note
 > 
 >  
 > 
 > This XML file can be reused for building other Java applications. It describes a common folder structure in the lines 3 - 12 and common targets for compiling and running the application.
 > 
 > When reusing this XML don’t forget to modify the project name in the line 1, that is also the name of the main class (line 14). The paths to OpenCV jar and jni lib are expected as parameters ("$\{ocvJarDir\}" in line 5 and "$\{ocvLibDir\}" in line 37), but you can hardcode these paths for your convenience. See [Ant documentation][] for detailed description of its build file format.
 * Create an src folder next to the build.xml file and a SimpleSample.java file in it.
 * Put the following Java code into the  SimpleSample.java file:
 
 import org.opencv.core.Mat;
 import org.opencv.core.CvType;
 import org.opencv.core.Scalar;
 
 class SimpleSample {
 
 
 static{
 System.loadLibrary("opencv_java244"); }
 
 public static void main(String[] args) {
 
 Mat m = new Mat(5, 10, CvType.CV_8UC1, new Scalar(0));
 System.out.println("OpenCV Mat: " + m);
 Mat mr1 = m.row(1);
 mr1.setTo(new Scalar(1));
 Mat mc5 = m.col(5);
 mc5.setTo(new Scalar(5));
 System.out.println("OpenCV Mat data:\n" + m.dump());
 }
 
 }
 * Run the following command in console in the folder containing  build.xml:
 
 ant -DocvJarDir=path/to/dir/containing/opencv-244.jar -DocvLibDir=path/to/dir/containing/opencv_java244/native/library
 
 For example:
 
 ant -DocvJarDir=X:\opencv-2.4.4\bin -DocvLibDir=X:\opencv-2.4.4\bin\Release
 
 The command should initiate \[re\]building and running the sample. You should see on the screen something like this:
 
 ![run app with Ant][]

# Create a simple Java project in Eclipse #

Now let’s look at the possiblity of using OpenCV in Java when developing in Eclipse IDE.

*  Create a new Eclipse workspace
 *  Create a new Java project via File –> New –> Java Project
    
    > ![Eclipse: new Java project][Eclipse_ new Java project]
    > 
    > Call it say “HelloCV”.
 *  Open  Java Build Path tab on  Project Properties dialog
    
    > and configure additional library (OpenCV) reference (jar and native library location):
    > 
    > ![Eclipse: external JAR][Eclipse_ external JAR]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 1]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 2]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 3]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 4]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 5]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 6]
    
    \` \`
    
    > ![Eclipse: external JAR][Eclipse_ external JAR 7]
    
    \` \`
 *  Add a new Java class (say Main) containing the application entry:
    
    > ![Eclipse: Main class][Eclipse_ Main class]
 *  Put some simple OpenCV calls there, e.g.:
    
        import org.opencv.core.CvType;
        import org.opencv.core.Mat;
        
        public class Main {
                  
            public static void main(String[] args) {
                  
                System.loadLibrary("opencv_java244");
                Mat m  = Mat.eye(3, 3, CvType.CV_8UC1);
                System.out.println("m = " + m.dump());
            }
        }
 *  Press Run button and find the identity matrix content in the Eclipse Console window.
    
    > ![Eclipse: run][Eclipse_ run]

# Create an SBT project and samples in Java and Scala #

Now we’ll create a simple Java application using SBT. This serves as a brief introduction to those unfamiliar with this build tool. We’re using SBT because it is particularly easy and powerful.

First, download and install [SBT][Simple Build Tool _SBT] using the instructions on its [web site][Simple Build Tool _SBT].

Next, navigate to a new directory where you’d like the application source to live (outside opencv dir). Let’s call it “JavaSample” and create a directory for it:

> cd <somewhere outside opencv>
> mkdir JavaSample

Now we will create the necessary folders and an SBT project:

>     cd JavaSample
>     mkdir -p src/main/java # This is where SBT expects to find Java sources
>     mkdir project # This is where the build definitions live

Now open project/build.scala in your favorite editor and paste the following. It defines your project:

>     import sbt._
>      import Keys._
>     
>     object JavaSampleBuild extends Build {
>            
>       def scalaSettings = Seq(
>         scalaVersion := "2.10.0",
>         scalacOptions ++= Seq(
>           "-optimize",
>           "-unchecked",
>           "-deprecation"
>         )
>       )
>     
>       def buildSettings =
>         Project.defaultSettings ++
>         scalaSettings
>     
>       lazy val root = {
>            
>         val settings = buildSettings ++ Seq(name := "JavaSample")
>         Project(id = "JavaSample", base = file("."), settings = settings)
>       }
>     }

Now edit project/plugins.sbt and paste the following. This will enable auto-generation of an Eclipse project:

>     addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "2.1.0")

Now run sbt from the JavaSample root and from within SBT run eclipse to generate an eclipse project:

>     sbt # Starts the sbt console
>     > eclipse # Running "eclipse" from within the sbt console

You should see something like this:

> ![SBT output][]

You can now import the SBT project to Eclipse using Import ... -> Existing projects into workspace. Whether you actually do this is optional for the guide; we’ll be using SBT to build the project, so if you choose to use Eclipse it will just serve as a text editor.

To test that everything is working, create a simple “Hello OpenCV” application. Do this by creating a file src/main/java/HelloOpenCV.java with the following contents:

>     public class HelloOpenCV {
>            
>        public static void main(String[] args) {
>            
>          System.out.println("Hello, OpenCV");
>       }
>     }

Now execute run from the sbt console, or more concisely, run sbt run from the command line:

>     sbt run

You should see something like this:

> ![SBT run][]

# Copy the OpenCV jar and write a simple application #

Now we’ll create a simple face detection application using OpenCV.

First, create a lib/ folder and copy the OpenCV jar into it. By default, SBT adds jars in the lib folder to the Java library search path. You can optionally rerun sbt eclipse to update your Eclipse project.

> mkdir lib
> cp <opencv_dir>/build/bin/opencv_<version>.jar lib/
> sbt eclipse

Next, create the directory src/main/resources and download this Lena image into it:

> ![Lena][]

Make sure it’s called "lena.png". Items in the resources directory are available to the Java application at runtime.

Next, copy lbpcascade\_frontalface.xml from opencv/data/ into the resources directory:

> cp <opencv_dir>/data/lbpcascades/lbpcascade_frontalface.xml src/main/resources/

Now modify src/main/java/HelloOpenCV.java so it contains the following Java code:

import org.opencv.core.Core;
    import org.opencv.core.Mat;
    import org.opencv.core.MatOfRect;
    import org.opencv.core.Point;
    import org.opencv.core.Rect;
    import org.opencv.core.Scalar;
    import org.opencv.highgui.Highgui;
    import org.opencv.objdetect.CascadeClassifier;
    
    //
    // Detects faces in an image, draws boxes around them, and writes the results
    // to "faceDetection.png".
    //
    class DetectFaceDemo {
          
      public void run() {
          
        System.out.println("\nRunning DetectFaceDemo");
    
        // Create a face detector from the cascade file in the resources
        // directory.
        CascadeClassifier faceDetector = new CascadeClassifier(getClass().getResource("/lbpcascade_frontalface.xml").getPath());
        Mat image = Highgui.imread(getClass().getResource("/lena.png").getPath());
    
        // Detect faces in the image.
        // MatOfRect is a special container class for Rect.
        MatOfRect faceDetections = new MatOfRect();
        faceDetector.detectMultiScale(image, faceDetections);
    
        System.out.println(String.format("Detected %s faces", faceDetections.toArray().length));
    
        // Draw a bounding box around each face.
        for (Rect rect : faceDetections.toArray()) {
          
            Core.rectangle(image, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(0, 255, 0));
        }
    
        // Save the visualized detection.
        String filename = "faceDetection.png";
        System.out.println(String.format("Writing %s", filename));
        Highgui.imwrite(filename, image);
      }
    }
    
    public class HelloOpenCV {
          
      public static void main(String[] args) {
          
        System.out.println("Hello, OpenCV");
    
        // Load the native library.
        System.loadLibrary("opencv_java244");
        new DetectFaceDemo().run();
      }
    }

Note the call to System.loadLibrary("opencv\_java244"). This command must be executed exactly once per Java process prior to using any native OpenCV methods. If you don’t call it, you will getUnsatisfiedLink errors. You will also get errors if you try to load OpenCV when it has already been loaded.

Now run the face detection app using sbt run:

>     sbt run

You should see something like this:

> ![SBT run][SBT run 1]

It should also write the following image to faceDetection.png:

> ![Detected face][]

You’re done! Now you have a sample Java application working with OpenCV, so you can start the work on your own. We wish you good luck and many years of joyful life!

[Eclipse]: http://eclipse.org/
[Apache Ant]: http://ant.apache.org/
[Simple Build Tool _SBT]: http://www.scala-sbt.org/
[Introduction into Android Development]: http://docs.opencv.org/2.4.4-beta/doc/tutorials/introduction/android_binary_package/android_dev_intro.html#android-dev-intro
[OpenCV SourceForge repository]: http://sourceforge.net/projects/opencvlibrary/files/
[OpenCV git repository]: https://github.com/Itseez/opencv/
[Oracle_Sun JDK 6 or 7]: http://www.oracle.com/technetwork/java/javase/downloads/
[CMake output]: http://docs.opencv.org/2.4.4-beta/_images/cmake_output.png
[Ant documentation]: http://ant.apache.org/manual/
[run app with Ant]: http://docs.opencv.org/2.4.4-beta/_images/ant_output.png
[Eclipse_ new Java project]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_new_java_prj.png
[Eclipse_ external JAR]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib.png
[Eclipse_ external JAR 1]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib2.png
[Eclipse_ external JAR 2]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib3.png
[Eclipse_ external JAR 3]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib4.png
[Eclipse_ external JAR 4]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib5.png
[Eclipse_ external JAR 5]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib6.png
[Eclipse_ external JAR 6]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib7.png
[Eclipse_ external JAR 7]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_user_lib8.png
[Eclipse_ Main class]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_main_class.png
[Eclipse_ run]: http://docs.opencv.org/2.4.4-beta/_images/eclipse_run.png
[SBT output]: http://docs.opencv.org/2.4.4-beta/_images/sbt_eclipse.png
[SBT run]: http://docs.opencv.org/2.4.4-beta/_images/sbt_run.png
[Lena]: http://docs.opencv.org/2.4.4-beta/_images/lena.png
[SBT run 1]: http://docs.opencv.org/2.4.4-beta/_images/sbt_run_face.png
[Detected face]: http://docs.opencv.org/2.4.4-beta/_images/faceDetection.png