android 通过摄像头手指测量心率的代码

以下是一个简单的使用 Android 相机 API 和 OpenCV 库来实现手指心率测量的示例代码：

public class HeartRateMonitorActivity extends AppCompatActivity implements Camera.PreviewCallback {

    private static final int CAMERA_PERMISSION_REQUEST_CODE = 100;
    private static final int CAMERA_FRAME_WIDTH = 640;
    private static final int CAMERA_FRAME_HEIGHT = 480;
    private static final int MAX_FRAME_SIZE = CAMERA_FRAME_WIDTH * CAMERA_FRAME_HEIGHT;

    private Camera mCamera;
    private int[] mRgbData = new int[MAX_FRAME_SIZE];
    private int[] mGrayData = new int[MAX_FRAME_SIZE];
    private Mat mRgbMat = new Mat(CAMERA_FRAME_HEIGHT, CAMERA_FRAME_WIDTH, CvType.CV_8UC4);
    private Mat mGrayMat = new Mat(CAMERA_FRAME_HEIGHT, CAMERA_FRAME_WIDTH, CvType.CV_8UC1);
    private TextView mHeartRateTextView;

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

        mHeartRateTextView = findViewById(R.id.heart_rate_text_view);

        if (checkSelfPermission(Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
            startCamera();
        } else {
            requestPermissions(new String[]{Manifest.permission.CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        stopCamera();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            startCamera();
        }
    }

    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        // Convert the camera image data to RGB format
        Camera.Parameters parameters = camera.getParameters();
        int imageFormat = parameters.getPreviewFormat();
        if (imageFormat == ImageFormat.NV21) {
            ImageProcessing.convertNv21ToRgb(data, mRgbData, CAMERA_FRAME_WIDTH, CAMERA_FRAME_HEIGHT);
        } else {
            ImageProcessing.convertYv12ToRgb(data, mRgbData, CAMERA_FRAME_WIDTH, CAMERA_FRAME_HEIGHT);
        }
        mRgbMat.put(0, 0, mRgbData);

        // Convert the RGB image to grayscale
        Imgproc.cvtColor(mRgbMat, mGrayMat, Imgproc.COLOR_RGB2GRAY);

        // Apply a Gaussian blur to the grayscale image to reduce noise
        Imgproc.GaussianBlur(mGrayMat, mGrayMat, new Size(15, 15), 0);

        // Compute the average pixel intensity of the grayscale image
        double average = Core.mean(mGrayMat).val[0];

        // Update the heart rate display based on the average pixel intensity
        int heartRate = (int) (60 * (average / 255.0));
        mHeartRateTextView.setText(String.valueOf(heartRate));
    }

    private void startCamera() {
        mCamera = Camera.open();
        mCamera.setPreviewCallback(this);
        Camera.Parameters parameters = mCamera.getParameters();
        parameters.setPreviewSize(CAMERA_FRAME_WIDTH, CAMERA_FRAME_HEIGHT);
        parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO);
        mCamera.setParameters(parameters);
        mCamera.startPreview();
    }

    private void stopCamera() {
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.setPreviewCallback(null);
            mCamera.release();
            mCamera = null;
        }
    }
}

该示例代码包含以下步骤：

1. 检查相机权限，如果已经获得相机权限则启动相机，否则请求相机权限。
2. 在 `onPreviewFrame()` 方法中，将相机图像数据从 YUV 格式转换为 RGB 格式，并将 RGB 数据填充到 OpenCV 的 `Mat` 对象中。
3. 将 RGB 图像转换为灰度图像，并对其进行高斯模糊以降低噪声。
4. 计算灰度图像的平均像素强度，并将其转换为心率值。
5. 在 UI 界面上更新心率显示。

请注意，该示例代码仅用于演示目的，实际应用中可能需要进行更多的优化和调整。