问题解决的关键在于使用Android NDK中的本地方法,以C/C++代码编写来处理图像,同时还需要使用Android系统控件来获取相机预览图像。以下是具体的和代码示例:
1.创建一个Android Studio项目,然后在项目中添加一个jni文件夹,并在其中创建一个名为“native-lib.cpp”的C++文件。
2.在“build.gradle(Module:app)”文件中添加以下代码:
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
3.在“build.gradle(Module:app)”文件中添加以下代码,用于导入OpenCV库:
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'org.opencv:opencv-android:3.1.0'
}
4.在“CMakeLists.txt”文件中添加以下代码:
cmake_minimum_required(VERSION 3.4.1)
add_library(native-lib SHARED native-lib.cpp)
find_library(log-lib log)
target_link_libraries(native-lib ${log-lib} -ljnigraphics -lopencv_android_core -lopencv_java3)
5.在“MainActivity.java”文件中添加以下代码:
public class MainActivity extends AppCompatActivity {
static {
System.loadLibrary("native-lib");
}
private Camera mCamera;
private CameraPreview mPreview;
private FrameLayout mLayout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mLayout = findViewById(R.id.camera_preview);
mPreview = new CameraPreview(this, mCamera);
mLayout.addView(mPreview);
Button captureButton = findViewById(R.id.button_capture);
captureButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
captureImage();
}
});
}
private void captureImage() {
mCamera.takePicture(null, null, new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
modifyImage(bitmap);
}
});
}
private void modifyImage(Bitmap bitmap) {
Bitmap modifiedBitmap = doSomethingWithBitmap(bitmap);
ImageView imageView = findViewById(R.id.image_view);
imageView.setImageBitmap(modifiedBitmap);
}
public static native void doSomethingWithImage(long matAddress);
}
6.在“CameraPreview.java”文件中添加以下代码:
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
mHolder = getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d("CameraPreview", "Error setting camera preview: " + e.getMessage());
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
if (mHolder.getSurface() == null) {
return;
}
try {
mCamera.stopPreview();
} catch (Exception e) {
}
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e) {
Log.d("CameraPreview", "Error starting camera preview: " + e.getMessage());
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
try {
mCamera.stopPreview();
mCamera.release();
} catch (Exception e) {
}
}
}
7.在“native-lib.cpp”文件中添加以下代码: