Android 相机预览看起来很奇怪

Question

我正在实现一个相机应用程序，当我查看预览时(尤其是使用前置摄像头时)，图像非常胖。看起来图像被水平拉伸(stretch)了。我按照 sdk 示例使用优化的相机尺寸，但它没有帮助。如何调整我的相机设置，使其像其他相机应用程序一样预览？

谢谢。

我的代码如下。

public class CameraActivity extends Activity implements SurfaceHolder.Callback, Camera.ShutterCallback, Camera.PictureCallback {

Camera m_camera;
SurfaceView m_surfaceView;
int m_numOfCamera;
int m_defaultCameraId;
int m_currentCamera;
int m_surfaceWidth;
int m_surfaceHeight;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_camera);
    getActionBar().setDisplayHomeAsUpEnabled(true);


    m_surfaceView = (SurfaceView)findViewById(R.id.cameraPreview);
    m_surfaceView.getHolder().addCallback(this);

    m_camera = Camera.open();

    m_numOfCamera = Camera.getNumberOfCameras();

    CameraInfo cameraInfo = new CameraInfo();
    for (int i = 0; i < m_numOfCamera; ++i) {
        Camera.getCameraInfo(i, cameraInfo);
        if (cameraInfo.facing == CameraInfo.CAMERA_FACING_BACK) {
            m_defaultCameraId = i;
            m_currentCamera = m_defaultCameraId;
        }       
    }

    if (m_numOfCamera < 1) {
        MenuItem switchCam = (MenuItem)findViewById(R.id.menu_switch_camera);
        switchCam.setVisible(false);
    }
}

@Override
public void onPause() {
    super.onPause();
    m_camera.stopPreview();
}

@Override
public void onDestroy() {
    super.onDestroy();
    m_camera.release();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_camera, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(final MenuItem item) 
{
    if (item.getItemId() == android.R.id.home) 
    {
        Intent intent = new Intent(this, MainActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(intent);

        return true;
    } 
    else if (item.getItemId() == R.id.menu_switch_camera)
    {
        if (m_camera != null) {
            m_camera.stopPreview();
            m_camera.release();
            m_camera = null;
        }   

        m_camera = Camera.open((m_currentCamera + 1) % m_numOfCamera);
        m_currentCamera = (m_currentCamera + 1) % m_numOfCamera;

        Camera.Parameters params = m_camera.getParameters();
        List<Camera.Size> sizes = params.getSupportedPreviewSizes();
        Camera.Size size = getOptimalPreviewSize(sizes, m_surfaceWidth, m_surfaceHeight);

        params.setPreviewSize(size.width,  size.height);

        m_camera.setParameters(params);
        setCameraDisplayOrientation(this, m_currentCamera, m_camera);
        m_camera.startPreview();
        try {
            m_camera.setPreviewDisplay(m_surfaceView.getHolder());
        } catch (Exception e) {
            e.printStackTrace();
        }   
        return true;
    }
    return true;
}

public void onPictureTaken(byte[] arg0, Camera arg1) {
    // TODO Auto-generated method stub

}

public void onShutter() {
    // TODO Auto-generated method stub

}

public void surfaceChanged(SurfaceHolder arg0, int format, int w, int h) {
    m_surfaceWidth = w;
    m_surfaceHeight = h;
    Camera.Parameters params = m_camera.getParameters();
    List<Camera.Size> sizes = params.getSupportedPreviewSizes();
    Camera.Size selected = getOptimalPreviewSize(sizes, w, h);

    params.setPreviewSize(selected.width,  selected.height);


    m_camera.setParameters(params);
    setCameraDisplayOrientation(this, m_currentCamera, m_camera);
    m_camera.startPreview();    
}

private static void setCameraDisplayOrientation(Activity activity,
         int cameraId, android.hardware.Camera camera) {
     android.hardware.Camera.CameraInfo info =
             new android.hardware.Camera.CameraInfo();
     android.hardware.Camera.getCameraInfo(cameraId, info);
     int rotation = activity.getWindowManager().getDefaultDisplay()
             .getRotation();
     int degrees = 0;
     switch (rotation) {
         case Surface.ROTATION_0: degrees = 0; break;
         case Surface.ROTATION_90: degrees = 90; break;
         case Surface.ROTATION_180: degrees = 180; break;
         case Surface.ROTATION_270: degrees = 270; break;
     }

     int result;
     if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
         result = (info.orientation + degrees) % 360;
         result = (360 - result) % 360;  // compensate the mirror
     } else {  // back-facing
         result = (info.orientation - degrees + 360) % 360;
     }
     camera.setDisplayOrientation(result);
 }


public void surfaceCreated(SurfaceHolder arg0) {
    try {
        m_camera.setPreviewDisplay(m_surfaceView.getHolder());
    } catch (Exception e) {
        e.printStackTrace();
    }   
}

public void surfaceDestroyed(SurfaceHolder arg0) {
    // TODO Auto-generated method stub

}

private Size getOptimalPreviewSize(List<Size> sizes, int w, int h) {


    final double ASPECT_TOLERANCE = 0.1;
    double targetRatio = (double) w / h;
    if (sizes == null)
        return null;

    Size optimalSize = null;
    double minDiff = Double.MAX_VALUE;

    int targetHeight = h;

    // Try to find an size match aspect ratio and size
    for (Size size : sizes) {
        double ratio = (double) size.width / size.height;
        if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE)
            continue;
        if (Math.abs(size.height - targetHeight) < minDiff) {
            optimalSize = size;
            minDiff = Math.abs(size.height - targetHeight);
        }
    }

    // Cannot find the one match the aspect ratio, ignore the requirement
    if (optimalSize == null) {
        minDiff = Double.MAX_VALUE;
        for (Size size : sizes) {
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }
    }

    return optimalSize;
}

}

Answer 1

相机预览总是填满显示它的 SurfaceView。如果 m_surfaceView 的纵横比与相机的纵横比不匹配，预览将被拉伸(stretch)。

您需要创建匹配宽高比的 m_surfaceView。这意味着，您需要从代码而不是布局 XML 文件创建它。

您可以在 android 示例项目中找到一个示例项目 APIDemos。在项目中有一个名为 CameraPreview 的东西。这对在 SurfaceView 中设置相机预览有很好的演示。它有一个 extends ViewGroup 的类，并从代码中添加 SurfaceView 作为其子级。 onMeasure() 方法已被覆盖以确定 SurfaceView 的高度和宽度，因此纵横比得以保留。看看这个项目，我希望它会很清楚。

[抱歉，我无法在此处发布链接 - this应该是链接，但我发现它坏了。但是如果你已经安装了带有 Android SDK 的示例项目，你可以在示例中找到该项目。打开一个新的 Android 示例项目，选择 APIDemos，然后查找名为 CameraPreview 的类。据我所知，它应该在 com.example.android.apis.graphics 包中。]