package org.opencv.imgcodecs does not exist && package org.opencv.videoio does not exist in a java opencv project with gradle

I'am under ubuntu 20.04

here is my gradle settings :

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
    implementation "joda-time:joda-time:2.2"
    implementation "junit:junit:4.12"
    implementation 'com.google.code.gson:gson:2.9.0'
    implementation 'org.apache.commons:commons-lang3:3.5'
    testImplementation 'junit:junit:4.13'
  implementation 'org.apache.logging.log4j:log4j-api:2.18.0'
  implementation 'org.apache.logging.log4j:log4j-core:2.18.0'
  implementation "nu.pattern:opencv:2.4.9-7"


}

And my App.java :

/*
 * This Java source file was generated by the Gradle 'init' task.
 */
package silentevil;


import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.CvType;
import org.opencv.core.Scalar;
import nu.pattern.OpenCV;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import org.opencv.core.MatOfByte;
import org.opencv.core.Size;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
import org.opencv.videoio.VideoCapture;



public class App {
    public static void loadOpenCVNativeLibrary() {
        nu.pattern.OpenCV.loadShared();
        //nu.pattern.OpenCV.loadLocally();
        }
    public String getGreeting() {
        return "Hello World!";
    }

    public static void main(String[] args) {
        OpenCV.loadLocally();
        System.out.println("Welcome to OpenCV " + Core.VERSION);
        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());
        System.out.println(new App().getGreeting());
    }
}

Without the import org.opencv.imgcodecs.Imgcodecs; and the import org.opencv.videoio.VideoCapture;

It works but i would like to test the webcam.

I have these errors :

App.java:21: error: package org.opencv.imgcodecs does not exist
import org.opencv.imgcodecs.Imgcodecs;
                           ^
App.java:23: error: package org.opencv.videoio does not exist
import org.opencv.videoio.VideoCapture;

How can in install theses libs or why are they not included ?

edit :

I've also tried to import a compiled jar with gradle :

dependencies {
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
    implementation "joda-time:joda-time:2.2"
    implementation "junit:junit:4.12"
    implementation 'com.google.code.gson:gson:2.9.0'
    implementation 'org.apache.commons:commons-lang3:3.5'
    testImplementation 'junit:junit:4.13'
  implementation 'org.apache.logging.log4j:log4j-api:2.18.0'
  implementation 'org.apache.logging.log4j:log4j-core:2.18.0'
  //implementation "nu.pattern:opencv:2.4.9-7"
  implementation files('lib/opencv-460.jar')


}

i've changed my code also :

package silentevil;

//import nu.pattern.OpenCV;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.CvType;
import org.opencv.core.Scalar;

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.InputStream;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import org.opencv.core.MatOfByte;
import org.opencv.core.Size;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;
import org.opencv.videoio.VideoCapture;



public class App {
    public static void loadOpenCVNativeLibrary() {
        //nu.pattern.OpenCV.loadShared();
        //nu.pattern.OpenCV.loadLocally();
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        }
    public String getGreeting() {
        return "Hello World!";
    }

    public static void main(String[] args) {
        //OpenCV.loadLocally();
        System.out.println("Welcome to OpenCV " + Core.VERSION);
        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());
        System.out.println(new App().getGreeting());
    }
}

but when i do the import jar with gradle i have this error :

Exception in thread "main" java.lang.UnsatisfiedLinkError: 'long org.opencv.core.Mat.n_Mat(int, int, int, double, double, double, double)'
    at org.opencv.core.Mat.n_Mat(Native Method)
    at org.opencv.core.Mat.<init>(Mat.java:77)
    at silentevil.App.main(App.java:40)

regards