Android - 实时从相机获取图像数据？

Question

我想做一些图像处理工作，我想从我的相机获取实时图像数据（在预览状态期间），而不是在拍照之后。

我看过这个post，但不知道如何使用它。

设置后，

SurfaceHolder.Callback surfaceCallback=new SurfaceHolder.Callback() 
{   
    public void surfaceCreated(SurfaceHolder holder) {
       camera.setPreviewCallback(previewCallback);
    }
}

还有这个

private Camera.PreviewCallback  previewCallback= new Camera.PreviewCallback()
{   
    @Override
    public void onPreviewFrame(byte[] data,Camera cam)
    {
            Camera.Size previewSize = cam.getParameters().getPreviewSize();
            YuvImage yuvImage = new YuvImage(data, ImageFormat.NV21,previewSize.width,previewSize.height, null);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            yuvImage.compressToJpeg(new Rect(0,0,previewSize.width,previewSize.height),80,baos);
            byte[] jdata = baos.toByteArray();
            Bitmap bitmap = BitmapFactory.decodeByteArray(jdata,0,jdata.length);    
    }
};

如何实时获取我的图像数据？谁能给我一个简短的示例代码？

谢谢

Answer 1

对于基于图像处理的操作，您可以使用 OpenCV 库。 这里我给出了使用 OpenCV 直接从相机处理帧的示例代码

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.JavaCameraView;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Mat;

import static org.opencv.core.CvType.CV_8UC1;

public class MainActivity extends AppCompatActivity implements CameraBridgeViewBase.CvCameraViewListener2 {

    private static final String TAG = "MainActivity";
    JavaCameraView javaCameraView;
    Mat frame;
    public static final int CAMERA_PERMISSION_REQUEST_CODE = 3;

    static {
        System.loadLibrary("MyOpenCVLibs");
    }

    private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch(status){
                case LoaderCallbackInterface.SUCCESS:
                {
                    javaCameraView.enableView();
                } break;
                default:
                {
                    super.onManagerConnected(status);
                } break;
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (ContextCompat.checkSelfPermission(this,Manifest.permission.CAMERA)!= PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA},CAMERA_PERMISSION_REQUEST_CODE);
        }

        javaCameraView = (JavaCameraView) findViewById(R.id.java_camera_view);
        javaCameraView.setVisibility(View.VISIBLE);
        javaCameraView.setCvCameraViewListener(this);
    }

    @Override
    protected void onPause(){
        super.onPause();
        if(javaCameraView!=null)
            javaCameraView.disableView();
    }

    @Override
    protected void onDestroy(){
        super.onDestroy();
        if(javaCameraView!=null)
            javaCameraView.disableView();
    }

    @Override
    protected void  onResume(){

        super.onResume();
        if (OpenCVLoader.initDebug()) {
            Log.i(TAG, "OpenCV loaded successfully.");
            mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
        } else {
            Log.i(TAG, "OpenCV not loaded.");
            OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_1_0, this, mLoaderCallback);
        }
    }

    @Override
    public void onCameraViewStarted(int width, int height) {
        frame=new Mat(height,width,CV_8UC4);

    }

    @Override
    public void onCameraViewStopped() {
        frame.release();
    }

    @Override
    public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
        frame=inputFrame.rgba();

    }
} 

• 此代码检查 OpenCV 是否正确导入并检查相机的权限。
• 并且每个输入帧都保存在帧变量中。