在Java中使用OpenCV (maven,ant,eclipse)

Java中使用OpenCV

从2.4.4开始，OpenCV支持Java. 
参考链接： http://docs.opencv.org/doc/tutorials/introduction/desktopjava/javadev_intro.html

获取OpenCV

从SourceForge可以获得依赖的文件。当然Windows用户最简单的方式是下载.exe文件安装。

对Window用户，在opencv/build/java/文件夹下有所需的jar文件。对于其他用户，需要使用源文件进行编译。

Java Sample With eclipse

在eclipse中使用Opencv，最简单的方式是在eclipse中建立一个用户Library。每次在使用opencv时，引入该Library。

来源：http://docs.opencv.org/doc/tutorials/introduction/javaeclipse/javaeclipse.html#java-eclipse

步骤： 
1,Launch Eclipse and select Window –> Preferences from the menu. 
2,Navigate under Java –> Build Path –> User Libraries and click New.... 
3,Enter a name, e.g. OpenCV-2.4.6, for your new library. 
4,Now select your new user library and click Add External JARs.... 
5,Browse through C:\OpenCV-2.4.6\build\java\ and select opencv-246.jar. After adding the jar, extend the opencv-246.jar and selectNative library location and press Edit.... 
6,Select External Folder... and browse to select the folder C:\OpenCV-2.4.6\build\java\x64. If you have a 32-bit system you need to select the x86 folder instead of x64. 
7,Now start creating a new Java project.On the Java Settings step, under Libraries tab, select Add Library... and select OpenCV-2.4.6, then clickFinish.

Demo

public class SampleCV {

    public static void main(String[] args) {

        System.loadLibrary( Core.NATIVE_LIBRARY_NAME );

        //读取图像，不改变图像的原始信息
        Mat m = Highgui.imread("c:\\1.png",Highgui.CV_LOAD_IMAGE_COLOR);

        //将图片转换成灰度图片
        Mat gray = new Mat(m.size(),CvType.CV_8UC1);
        Imgproc.cvtColor(m,gray,Imgproc.COLOR_RGB2GRAY);

        //计算灰度直方图
        List<Mat> images = new ArrayList<Mat>();
        images.add(gray);

        MatOfInt channels= new MatOfInt(0);
        MatOfInt histSize = new MatOfInt(256);
        MatOfFloat ranges= new MatOfFloat(0,256);
        Mat hist = new Mat();
        Imgproc.calcHist(images, channels, new Mat(), hist, histSize, ranges);

        //mat求和
        System.out.println(Core.sumElems(hist));

        //保存转换的图片
        Highgui.imwrite("c:\\2.png",gray);

    }   
}

Java Sample with Maven

在pom.xml中添加opencv的依赖如下：

    <dependency>
        <groupId>org.opencv</groupId>
        <artifactId>opencv</artifactId>
        <version>2.4.9</version>
        <systemPath>C:/opencv/build/java/opencv-249.jar</systemPath>
        <scope>system</scope>
    </dependency>

然后在加载动态链接库时，不使用System.loadLibrary(xxx);。 而是使用 绝对路径加载：System.load(xxx);

将Demo中的System.loadLibrary(xxx);用如下的两句话替换，其他无需改变：

    String path = "C:\\opencv\\build\\java\\x64\\opencv_java249.dll";
    System.load(path);

Java Sample with Ant

建立下面的build.xml，执行ant命令：

ant -DocvJarDir=X:\opencv-2.4.4\bin -DocvLibDir=X:\opencv-2.4.4\bin\Release、

或者直接将DocvJarDir，DocvLibDir硬编码到build.xml。

build.xml文件：

       <property name="src.dir"     value="src"/>

       <property name="lib.dir"     value="${ocvJarDir}"/>
       <path id="classpath">
           <fileset dir="${lib.dir}" includes="**/*.jar"/>
       </path>

       <property name="build.dir"   value="build"/>
       <property name="classes.dir" value="${build.dir}/classes"/>
       <property name="jar.dir"     value="${build.dir}/jar"/>

       <property name="main-class"  value="${ant.project.name}"/>


       <target name="clean">
           <delete dir="${build.dir}"/>
       </target>

       <target name="compile">
           <mkdir dir="${classes.dir}"/>
           <javac includeantruntime="false" srcdir="${src.dir}" destdir="${classes.dir}" classpathref="classpath"/>
       </target>

       <target name="jar" depends="compile">
           <mkdir dir="${jar.dir}"/>
           <jar destfile="${jar.dir}/${ant.project.name}.jar" basedir="${classes.dir}">
               <manifest>
                   <attribute name="Main-Class" value="${main-class}"/>
               </manifest>
           </jar>
       </target>

       <target name="run" depends="jar">
           <java fork="true" classname="${main-class}">
               <sysproperty key="java.library.path" path="${ocvLibDir}"/>
               <classpath>
                   <path refid="classpath"/>
                   <path location="${jar.dir}/${ant.project.name}.jar"/>
               </classpath>
           </java>
       </target>

       <target name="rebuild" depends="clean,jar"/>

       <target name="rebuild-run" depends="clean,run"/>

   </project>