在自定义Camera2 API上显示矩形边界框（覆盖），以便仅捕获该框内的图像

时间：2019-03-05 15:27:33

标签： android preview android-camera2 camera-overlay

我正在使用以下代码通过自定义Camera2 API捕获图像。我是一个初学者，我不知道如何在相机预览中显示矩形叠加层。我确实尝试过这里提供的解决方案，但无法弄清楚如何使其适合我的代码。

我需要实现这样的功能来捕获A4纸。

Rectangular overlay

只有框中的图像部分必须被捕获并显示在下一个活动中。

MainActivity 

package com.example.customcamera;

import android.Manifest;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.ImageFormat;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.HandlerThread;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
    static
    {
        ORIENTATIONS.append(Surface.ROTATION_0, 90);
        ORIENTATIONS.append(Surface.ROTATION_90, 0);
        ORIENTATIONS.append(Surface.ROTATION_180, 270);
        ORIENTATIONS.append(Surface.ROTATION_270, 180);
    }

    TextureView textureView;
    private CameraDevice cameraDevice;
    private String cameraId;
    private Size imageDimensions;
    private CameraCaptureSession cameraCaptureSession;
    private CaptureRequest.Builder captureRequestBuilder;
    private ImageReader imageReader;
    private boolean flashSupported;
    private HandlerThread backgroundThread;
    private Handler backgroundHandler;


    CameraDevice.StateCallback stateCallback;
    File file;
    final int MY_PERMISSIONS_REQUEST_CAMERA=102;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        stateCallback = new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice camera) {
                cameraDevice = camera;
                createCameraPreview();
            }

            @Override
            public void onDisconnected(@NonNull CameraDevice cameraDevice) {
                MainActivity.this.cameraDevice.close();
            }

            @Override
            public void onError(@NonNull CameraDevice cameraDevice, int i) {
                MainActivity.this.cameraDevice.close();
                MainActivity.this.cameraDevice = null;        // Change to global
            }
        };

        textureView = findViewById(R.id.textureView);
        textureView.setSurfaceTextureListener(textureListener);

        Button btn_camera = findViewById(R.id.btn_camera);
        btn_camera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                takePicture();
            }
        });
    }

    public void takePicture()
    {
        if(cameraDevice == null)
            return;

        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        try
        {
            CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraDevice.getId());
            Size[] jpegSizes = null;

            if(cameraCharacteristics == null)
                jpegSizes = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP).getOutputSizes(ImageFormat.JPEG);

            // Capture image with custom size
            int width = 640;
            int height = 480;

            if(jpegSizes != null && jpegSizes.length > 0)
            {
                width = jpegSizes[0].getWidth();
                height = jpegSizes[0].getHeight();
            }

            imageReader = ImageReader.newInstance(width, height, ImageFormat.JPEG, 1);
            final List<Surface> outputSurface = new ArrayList<>(2);
            outputSurface.add(imageReader.getSurface());
            outputSurface.add(new Surface(textureView.getSurfaceTexture()));

            final CaptureRequest.Builder captureBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            captureBuilder.addTarget(imageReader.getSurface());
            captureBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);

            // Check orientation base on device
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));

            ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
                @Override
                public void onImageAvailable(ImageReader imageReader) {

                    file = new File(Environment.getExternalStorageDirectory() + "/" + UUID.randomUUID().toString() + ".jpg");
                    Image image = null;

                    try
                    {
                        image = imageReader.acquireLatestImage();
                        ByteBuffer buffer = image.getPlanes()[0].getBuffer();
                        buffer.rewind();
                        byte[] bytes = new byte[buffer.capacity()];
                        buffer.get(bytes);
                        save(bytes);

                        startActivity(new Intent(MainActivity.this, ImageDisplay.class).putExtra("FILE", file.getPath()));
                    }

                    finally {
                        if(image != null)
                            image.close();
                    }
                }

                public void save(byte[] bytes)
                {
                    OutputStream outputStream = null;

                    try
                    {
                        outputStream = new FileOutputStream(file);
                        outputStream.write(bytes);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if(outputStream == null) {
                            try {
                                outputStream.close();
                            } catch (IOException e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            };

            imageReader.setOnImageAvailableListener(readerListener, backgroundHandler);

            final CameraCaptureSession.CaptureCallback captureCallback = new CameraCaptureSession.CaptureCallback() {
                @Override
                public void onCaptureCompleted(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
                    super.onCaptureCompleted(session, request, result);
                    Toast.makeText(MainActivity.this, "Saved", Toast.LENGTH_SHORT).show();
                    createCameraPreview();
                }
            };

            cameraDevice.createCaptureSession(outputSurface, new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    try {
                        cameraCaptureSession.capture(captureBuilder.build(), captureCallback, backgroundHandler);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {

                }
            }, backgroundHandler);
        }
        catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void createCameraPreview() {

        SurfaceTexture texture = textureView.getSurfaceTexture();
        assert texture != null;

        texture.setDefaultBufferSize(imageDimensions.getWidth(), imageDimensions.getHeight());
        Surface surface = new Surface(texture);
        try {
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder.addTarget(surface);

            cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession session) {
                    if(cameraDevice == null)
                        return;

                    cameraCaptureSession = session;
                    updatePreview();
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(MainActivity.this, "Changed", Toast.LENGTH_SHORT).show();
                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void updatePreview() {
        if(cameraDevice == null)
            Toast.makeText(MainActivity.this, "Error!", Toast.LENGTH_SHORT).show();

        captureRequestBuilder.set(CaptureRequest.CONTROL_MODE, CaptureRequest.CONTROL_MODE_AUTO);
        try {
            cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, backgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

    }

    private void openCamera()
    {
        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try
        {
            cameraId = cameraManager.getCameraIdList()[0];
            CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraId);
            StreamConfigurationMap map = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            assert map != null;
            imageDimensions = map.getOutputSizes(SurfaceTexture.class)[0];

            if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                // Permission to Camera is not granted, request for permission
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA,
                                Manifest.permission.WRITE_EXTERNAL_STORAGE},  MY_PERMISSIONS_REQUEST_CAMERA);
                return;
            }

            cameraManager.openCamera(cameraId, stateCallback, null);
        }
        catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int i, int i1) {
            openCamera();
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int i, int i1) {

        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {
            Log.e("Surfacetexturedestroyed", "called");
            if(cameraDevice != null)
            {
                Log.e("Camera not null", "make null");
                cameraDevice.close();
                cameraDevice = null;
            }
            return false;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {

        }
    };

    @Override
    protected void onResume() {
        super.onResume();

        startBackgroundThread();

        if(textureView.isAvailable())
            openCamera();
        else
            textureView.setSurfaceTextureListener(textureListener);
    }

    @Override
    protected void onPause() {
        stopBackgroundThread();
        super.onPause();
    }

    private void stopBackgroundThread() {
        backgroundThread.quitSafely();
        try {
            backgroundThread.join();
            backgroundThread = null;
            backgroundHandler = null;
        }
        catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private void startBackgroundThread() {
        backgroundThread = new HandlerThread("Camera Background");
        backgroundThread.start();
        backgroundHandler = new Handler(backgroundThread.getLooper());
    }

    /**
     * Handler for handling the user event after requesting permission.
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults)
    {
        switch (requestCode)
        {
            case 102:     //MY_PERMISSIONS_REQUEST_CAMERA=102   Use Camera

                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0  && grantResults[0] == PackageManager.PERMISSION_GRANTED)
                {
                    // permission was granted, yay!
                    openCamera();
                }
                else
                {
                    // permission denied, boo!
                    Toast.makeText(this, "Permission to use device Camera denied! Cannot proceed ahead!", Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;

            default: Toast.makeText(this, "Failed to handle permissions response!", Toast.LENGTH_SHORT).show();
        }
    }

}

activity_main.xml 

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextureView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:id="@+id/textureView"
        android:layout_alignParentTop="true"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Take Picture"
        android:textSize="30sp"
        android:id="@+id/btn_camera"
        android:layout_alignParentBottom="true"
        android:layout_margin="8dp"/>

</RelativeLayout>

ImageDisplay活动

package com.example.customcamera;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Path;
import android.media.Image;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;

import java.io.File;

public class ImageDisplay extends AppCompatActivity {

    ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.image_display);

        imageView = findViewById(R.id.imageView);

        String imgFile = getIntent().getStringExtra("FILE");

        Bitmap bitmap = BitmapFactory.decodeFile(imgFile);
        imageView.setImageBitmap(bitmap);
    }
}

image_display.xml 

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ImageDisplay">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

2 个答案:

答案 0 :(得分：0)

在onImageAvailableListener对象内部创建一个BitmapRegionDecoder对象。该对象带有一个矩形对象。创建矩形，使其仅保留ImageView边界。不要仅仅为了在ImageView的顶部显示ImageView而启动新的Activity。只需将图像视图添加到您的activity_main.xml中即可。确保将图像视图的高度和宽度设置为dp单位的实际数字。

要创建仅容纳图像视图边界的矩形，请创建显示指标对象，并使用指标对象查询设备的密度。因此，假设您的图像视图尺寸为300dp =宽度，200dp =高度，并且从指标对象返回的设备密度= 2.0 ...然后，将300 * 2.0和200 * 2.0相乘得到基于图像的边界框面积在您的设备密度上。由于您使用的是camera2 API，因此您必须根据SCALER配置请求知道预览区域是什么。使用这个已知区域和图像视图区域，您可以通过找到中心点来创建矩形（确保您的textureview的中心与imageview的中心重合。在xml中设置layout_gravity = center），然后使用一些基本的数学运算即可减去并增加图像视图的一半宽度和一半高度，以创建BitmapRegionDecoder对象所需的矩形对象。只需为BitmapRegionDecoder对象中所需的options参数传递null。您应该从解码器对象取回一些字节，然后可以将其转换为您选择的位图。

答案 1 :(得分：0)

我刚刚在Xamarin iOS App上做到了。如果发现有帮助，可以看看它。

Adding an CameraOverlayView

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