我尝试过Android Dev的简单代码。 （https://developer.android.com/guide/topics/media/camera.html）显示相机预览。但是，当我在手机上运行应用程序时，分辨率很低（模糊）。我的问题是如何提高分辨率？
我使用的代码写在下面
public class CameraApp extends AppCompatActivity {
Button captureButton;
private static final String TAG = CameraApp.class.getSimpleName();
private Camera mCamera;
private CameraPreview mPreview;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera_app);
// Create an instance of Camera
mCamera = getCameraInstance();
// Create our Preview view and set it as the content of our activity.
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
//previewHolder =
// Add a listener to the Capture button
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
// get an image from the camera
mCamera = getCameraInstance();
if (mCamera != null)
mCamera.takePicture(null, null, mPicture);
}
}
);
}
private Camera.PictureCallback mPicture = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
Intent saveImageIntent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
Uri savedImage = Uri.fromFile(pictureFile);
saveImageIntent.putExtra(MediaStore.EXTRA_OUTPUT, savedImage);
if (pictureFile == null) {
Log.d(TAG, "Error creating media file, check storage permissions: ");
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
fos.write(data);
fos.close();
} catch (FileNotFoundException e) {
Log.d(TAG, "File not found: " + e.getMessage());
} catch (IOException e) {
Log.d(TAG, "Error accessing file: " + e.getMessage());
}
camera.startPreview();
}
};
/**
* Check if this device has a camera
*/
/*
private boolean checkCameraHardware(Context context) {
if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}*/
/**
* A safe way to get an instance of the Camera object.
*/
public static Camera getCameraInstance() {
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
} catch (Exception e) {
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}
/**
* A basic Camera preview class
*/
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
if (mCamera != null) {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
}
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
//holder.getSurface().release();
if (mHolder.getSurface() == null) {
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e) {
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e) {
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
}
}
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
/**
* Create a file Uri for saving an image or video
*/
private static Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
/**
* Create a File for saving an image or video
*/
private static File getOutputMediaFile(int type) {
// To be safe, you should check that the SDCard is mounted
// using Environment.getExternalStorageState() before doing this.
File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_PICTURES), "MyCameraApp");
// This location works best if you want the created images to be shared
// between applications and persist after your app has been uninstalled.
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d("MyCameraApp", "failed to create directory");
return null;
}
mediaStorageDir.mkdirs();
}
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"IMG_" + timeStamp + ".jpg");
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator +
"VID_" + timeStamp + ".mp4");
} else {
return null;
}
return mediaFile;
}
}
答案 0 :(得分：2)
请按照 Picture distorted with Camera and getOptimalPreviewSize 进行操作，其中讨论了如何选择最适合您的屏幕（和布局）的支持预览尺寸。我给出了更多解释here。
在这里，我为后代粘贴了我发现的最好的implementation，感谢Shaked Klein Orbach：
private Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
final double ASPECT_TOLERANCE = 0.1;
double targetRatio = (double) h / w;
if (sizes == null) {
return null;
}
Camera.Size optimalSize = null;
double minDiff = Double.MAX_VALUE;
int targetHeight = h;
for (Camera.Size size : sizes) {
double ratio = (double) size.height / size.width;
if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) {
continue;
}
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
if (optimalSize == null) {
minDiff = Double.MAX_VALUE;
for (Camera.Size size : sizes) {
if (Math.abs(size.height - targetHeight) < minDiff) {
optimalSize = size;
minDiff = Math.abs(size.height - targetHeight);
}
}
}
return optimalSize;
}
请注意，您使用已弃用的 hardware.Camera API。如果您的代码主要针对较旧的（Lollipop之前的）设备，请考虑切换到新的 camera2 API。它可以产生更好的图像，并且其性能更好。但选择最佳预览分辨率的基本原则保持不变。