问题
I'm using the following code to capture an image using the custom Camera2 API. I am a beginner and I have no idea how to display a rectangular overlay on the camera preview. I did try the solutions available here, but I can't figure out how to fit it in my code.
I need to achieve something like this to capture A4 sheets.
Only the part of the image which is in the box must be captured and displayed in the next activity.
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 Activity
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>
回答1:
Inside your onImageAvailableListener object create a BitmapRegionDecoder object. This object takes a rectangle object. The rectangle is created so that It only holds the ImageView bounds. Don't start a new Activity just to show an ImageView on top of your TextureView. just add the image-view to your activity_main.xml. Make sure you set the image-view height and width to some actual number in dp units.
To create the rectangle that will hold only the bounds of your image-view, create a display metrics object and query the density of the device with the metrics objects. So, say your image-view dimensions are 300dp = width and 200dp = height and your device density returned from the metrics object = 2.0... Then, multiply 300 * 2.0 and 200 * 2.0 to get your image-view bounding box area based on your device density. Since you are using camera2 API, you must know what your preview area is based on the SCALER configuration request. Using this known area and your image-view area you create the rectangle by locating the center point(make sure the center of your textureview coincides with your imageview center. Set both layout_gravity = center in the xml) and then with some basic math you can subtract and add half the width and half the height of image-view to create the rectangle object your BitmapRegionDecoder object needs. Just pass null for the options parameter needed in the BitmapRegionDecoder object. You should get some bytes back from the decoder object which you can then turn into a bitmap of your choosing.
回答2:
I just did this on Xamarin iOS App. You can take a lookg at it incase if your found it helpful.
Adding an CameraOverlayView
来源：https://stackoverflow.com/questions/55006224/display-a-rectangular-bounding-box-overlay-on-custom-camera2-api-so-only-the-i