Android Camera SurfaceView 预览拍照

本文已获得作者授权,本文作者:cain_huang

原文链接:https://www.jianshu.com/p/9e0f3fc5a3b4

Android使用 Camera API + SurfaceView 方式进行预览拍照。

SurfaceView 的创建以及回调

创建一个SurfaceView,并实现SurfaceHolder的回调。

由于Camera在SurfaceView中是通过SurfaceHolder 使得Surfaceview能够预览Camera返回的数据,因此我们需要实现SurfaceHolder 的回调,实现代码如下:

public class CameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    private static final String TAG = CameraSurfaceView.class.getSimpleName();

    private SurfaceHolder mSurfaceHolder;

    public CameraSurfaceView(Context context) {
        super(context);
        init();
    }

    public CameraSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CameraSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mSurfaceHolder = getHolder();
        mSurfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        CameraUtils.openFrontalCamera(CameraUtils.DESIRED_PREVIEW_FPS);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        CameraUtils.startPreviewDisplay(holder);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        CameraUtils.releaseCamera();
    }
}

Camera 操作的辅助类

CameraUtils 辅助类主要是Camera API 的一些操作,比如打开相机、开始预览、停止预览、切换相机、设置预览参数等操作,具体实现如下:

public class CameraUtils {

    // 相机默认宽高,相机的宽度和高度跟屏幕坐标不一样,手机屏幕的宽度和高度是反过来的。
    public static final int DEFAULT_WIDTH = 1280;
    public static final int DEFAULT_HEIGHT = 720;
    public static final int DESIRED_PREVIEW_FPS = 30;

    private static int mCameraID = Camera.CameraInfo.CAMERA_FACING_FRONT;
    private static Camera mCamera;
    private static int mCameraPreviewFps;
    private static int mOrientation = 0;

    /**
     * 打开相机,默认打开前置相机
     * @param expectFps
     */
    public static void openFrontalCamera(int expectFps) {
        if (mCamera != null) {
            throw new RuntimeException("camera already initialized!");
        }
        Camera.CameraInfo info = new Camera.CameraInfo();
        int numCameras = Camera.getNumberOfCameras();
        for (int i = 0; i < numCameras; i++) {
            Camera.getCameraInfo(i, info);
            if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
                mCamera = Camera.open(i);
                mCameraID = info.facing;
                break;
            }
        }
        // 如果没有前置摄像头,则打开默认的后置摄像头
        if (mCamera == null) {
            mCamera = Camera.open();
            mCameraID = Camera.CameraInfo.CAMERA_FACING_BACK;
        }
        // 没有摄像头时,抛出异常
        if (mCamera == null) {
            throw new RuntimeException("Unable to open camera");
        }

        Camera.Parameters parameters = mCamera.getParameters();
        mCameraPreviewFps = CameraUtils.chooseFixedPreviewFps(parameters, expectFps * 1000);
        parameters.setRecordingHint(true);
        mCamera.setParameters(parameters);
        setPreviewSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
        setPictureSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
        mCamera.setDisplayOrientation(mOrientation);
    }

    /**
     * 根据ID打开相机
     * @param cameraID
     * @param expectFps
     */
    public static void openCamera(int cameraID, int expectFps) {
        if (mCamera != null) {
            throw new RuntimeException("camera already initialized!");
        }
        mCamera = Camera.open(cameraID);
        if (mCamera == null) {
            throw new RuntimeException("Unable to open camera");
        }
        mCameraID = cameraID;
        Camera.Parameters parameters = mCamera.getParameters();
        mCameraPreviewFps = CameraUtils.chooseFixedPreviewFps(parameters, expectFps * 1000);
        parameters.setRecordingHint(true);
        mCamera.setParameters(parameters);
        setPreviewSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
        setPictureSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
        mCamera.setDisplayOrientation(mOrientation);
    }

    /**
     * 开始预览
     * @param holder
     */
    public static void startPreviewDisplay(SurfaceHolder holder) {
        if (mCamera == null) {
            throw new IllegalStateException("Camera must be set when start preview");
        }
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 切换相机
     * @param cameraID
     */
    public static void switchCamera(int cameraID, SurfaceHolder holder) {
        if (mCameraID == cameraID) {
            return;
        }
        mCameraID = cameraID;
        // 释放原来的相机
        releaseCamera();
        // 打开相机
        openCamera(cameraID, CameraUtils.DESIRED_PREVIEW_FPS);
        // 打开预览
        startPreviewDisplay(holder);
    }

    /**
     * 释放相机
     */
    public static void releaseCamera() {
        if (mCamera != null) {
            mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }

    /**
     * 开始预览
     */
    public static void startPreview() {
        if (mCamera != null) {
            mCamera.startPreview();
        }
    }

    /**
     * 停止预览
     */
    public static void stopPreview() {
        if (mCamera != null) {
            mCamera.stopPreview();
        }
    }

    /**
     * 拍照
     */
    public static void takePicture(Camera.ShutterCallback shutterCallback,
                                   Camera.PictureCallback rawCallback,
                                   Camera.PictureCallback pictureCallback) {
        if (mCamera != null) {
            mCamera.takePicture(shutterCallback, rawCallback, pictureCallback);
        }
    }

    /**
     * 设置预览大小
     * @param camera
     * @param expectWidth
     * @param expectHeight
     */
    public static void setPreviewSize(Camera camera, int expectWidth, int expectHeight) {
        Camera.Parameters parameters = camera.getParameters();
        Camera.Size size = calculatePerfectSize(parameters.getSupportedPreviewSizes(),
                expectWidth, expectHeight);
        parameters.setPreviewSize(size.width, size.height);
        camera.setParameters(parameters);
    }

    /**
     * 获取预览大小
     * @return
     */
    public static Camera.Size getPreviewSize() {
        if (mCamera != null) {
            return mCamera.getParameters().getPreviewSize();
        }
        return null;
    }

    /**
     * 设置拍摄的照片大小
     * @param camera
     * @param expectWidth
     * @param expectHeight
     */
    public static void setPictureSize(Camera camera, int expectWidth, int expectHeight) {
        Camera.Parameters parameters = camera.getParameters();
        Camera.Size size = calculatePerfectSize(parameters.getSupportedPictureSizes(),
                expectWidth, expectHeight);
        parameters.setPictureSize(size.width, size.height);
        camera.setParameters(parameters);
    }

    /**
     * 获取照片大小
     * @return
     */
    public static Camera.Size getPictureSize() {
        if (mCamera != null) {
            return mCamera.getParameters().getPictureSize();
        }
        return null;
    }

    /**
     * 计算最完美的Size
     * @param sizes
     * @param expectWidth
     * @param expectHeight
     * @return
     */
    public static Camera.Size calculatePerfectSize(List<Camera.Size> sizes, int expectWidth,
                                                   int expectHeight) {
        sortList(sizes); // 根据宽度进行排序
        Camera.Size result = sizes.get(0);
        boolean widthOrHeight = false; // 判断存在宽或高相等的Size
        // 辗转计算宽高最接近的值
        for (Camera.Size size: sizes) {
            // 如果宽高相等,则直接返回
            if (size.width == expectWidth && size.height == expectHeight) {
                result = size;
                break;
            }
            // 仅仅是宽度相等,计算高度最接近的size
            if (size.width == expectWidth) {
                widthOrHeight = true;
                if (Math.abs(result.height - expectHeight)
                        > Math.abs(size.height - expectHeight)) {
                    result = size;
                }
            }
            // 高度相等,则计算宽度最接近的Size
            else if (size.height == expectHeight) {
                widthOrHeight = true;
                if (Math.abs(result.width - expectWidth)
                        > Math.abs(size.width - expectWidth)) {
                    result = size;
                }
            }
            // 如果之前的查找不存在宽或高相等的情况,则计算宽度和高度都最接近的期望值的Size
            else if (!widthOrHeight) {
                if (Math.abs(result.width - expectWidth)
                        > Math.abs(size.width - expectWidth)
                        && Math.abs(result.height - expectHeight)
                        > Math.abs(size.height - expectHeight)) {
                    result = size;
                }
            }
        }
        return result;
    }

    /**
     * 排序
     * @param list
     */
    private static void sortList(List<Camera.Size> list) {
        Collections.sort(list, new Comparator<Camera.Size>() {
            @Override
            public int compare(Camera.Size pre, Camera.Size after) {
                if (pre.width > after.width) {
                    return 1;
                } else if (pre.width < after.width) {
                    return -1;
                }
                return 0;
            }
        });
    }

    /**
     * 选择合适的FPS
     * @param parameters
     * @param expectedThoudandFps 期望的FPS
     * @return
     */
    public static int chooseFixedPreviewFps(Camera.Parameters parameters, int expectedThoudandFps) {
        List<int[]> supportedFps = parameters.getSupportedPreviewFpsRange();
        for (int[] entry : supportedFps) {
            if (entry[0] == entry[1] && entry[0] == expectedThoudandFps) {
                parameters.setPreviewFpsRange(entry[0], entry[1]);
                return entry[0];
            }
        }
        int[] temp = new int[2];
        int guess;
        parameters.getPreviewFpsRange(temp);
        if (temp[0] == temp[1]) {
            guess = temp[0];
        } else {
            guess = temp[1] / 2;
        }
        return guess;
    }

    /**
     * 设置预览角度,setDisplayOrientation本身只能改变预览的角度
     * previewFrameCallback以及拍摄出来的照片是不会发生改变的,拍摄出来的照片角度依旧不正常的
     * 拍摄的照片需要自行处理
     * 这里Nexus5X的相机简直没法吐槽,后置摄像头倒置了,切换摄像头之后就出现问题了。
     * @param activity
     */
    public static int calculateCameraPreviewOrientation(Activity activity) {
        Camera.CameraInfo info = new Camera.CameraInfo();
        Camera.getCameraInfo(mCameraID, 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;
        } else {
            result = (info.orientation - degrees + 360) % 360;
        }
        mOrientation = result;
        return result;
    }


    /**
     * 获取当前的Camera ID
     * @return
     */
    public static int getCameraID() {
        return mCameraID;
    }

    /**
     * 获取当前预览的角度
     * @return
     */
    public static int getPreviewOrientation() {
        return mOrientation;
    }

    /**
     * 获取FPS(千秒值)
     * @return
     */
    public static int getCameraPreviewThousandFps() {
        return mCameraPreviewFps;
    }
}

权限申请

在Activity中使用CameraSurfaceview,有Android6.0动态权限申请问题,需要我们判断相机和存储权限是否申请了:

public class CameraSurfaceViewActivity extends AppCompatActivity implements View.OnClickListener {

    private static final int REQUEST_CAMERA = 0x01;

    private CameraSurfaceView mCameraSurfaceView;
    private Button mBtnTake;
    private Button mBtnSwitch;

    private int mOrientation;

    // CameraSurfaceView 容器包装类
    private FrameLayout mAspectLayout;
    private boolean mCameraRequested;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_camera_surface);
        // Android 6.0相机动态权限检查
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                == PackageManager.PERMISSION_GRANTED) {
            initView();
        } else {
            ActivityCompat.requestPermissions(this,
                    new String[]{
                            Manifest.permission.CAMERA,
                            Manifest.permission.WRITE_EXTERNAL_STORAGE
                    }, REQUEST_CAMERA);
        }
    }

    /**
     * 初始化View
     */
    private void initView() {
        mAspectLayout = (FrameLayout) findViewById(R.id.layout_aspect);;
        mCameraSurfaceView = new CameraSurfaceView(this);
        mAspectLayout.addView(mCameraSurfaceView);
        mOrientation = CameraUtils.calculateCameraPreviewOrientation(CameraSurfaceViewActivity.this);
        mBtnTake = (Button) findViewById(R.id.btn_take);
        mBtnTake.setOnClickListener(this);
        mBtnSwitch = (Button) findViewById(R.id.btn_switch);
        mBtnSwitch.setOnClickListener(this);
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            // 相机权限
            case REQUEST_CAMERA:
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    mCameraRequested = true;
                    initView();
                }
                break;
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (mCameraRequested) {
            CameraUtils.startPreview();
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        CameraUtils.stopPreview();
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn_take:
                takePicture();
                break;

            case R.id.btn_switch:
                switchCamera();
                break;
        }
    }

    /**
     * 拍照
     */
    private void takePicture() {
        CameraUtils.takePicture(new Camera.ShutterCallback() {
            @Override
            public void onShutter() {

            }
        }, null, new Camera.PictureCallback() {
            @Override
            public void onPictureTaken(byte[] data, Camera camera) {
                CameraUtils.startPreview();
                Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
                if (bitmap != null) {
                    bitmap = ImageUtils.getRotatedBitmap(bitmap, mOrientation);
                    String path = Environment.getExternalStorageDirectory() + "/DCIM/Camera/"
                            + System.currentTimeMillis() + ".jpg";
                    try {
                        FileOutputStream fout = new FileOutputStream(path);
                        BufferedOutputStream bos = new BufferedOutputStream(fout);
                        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);
                        bos.flush();
                        bos.close();
                        fout.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                CameraUtils.startPreview();
            }
        });
    }


    /**
     * 切换相机
     */
    private void switchCamera() {
        if (mCameraSurfaceView != null) {
            CameraUtils.switchCamera(1 - CameraUtils.getCameraID(), mCameraSurfaceView.getHolder());
            // 切换相机后需要重新计算旋转角度
            mOrientation = CameraUtils.calculateCameraPreviewOrientation(CameraSurfaceViewActivity.this);
        }
    }

}

由于用到了相机和存储权限,我们需要在manifest中注册相机和存储权限,这里要说明的是,manifest用use-permission只是声明了需要使用哪些权限,而我们实际项目中在使用到这两项权限时,需要你检查权限是否已经被授权,如果没授权,则需要请求授权:

<!-- 存储权限 -->
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <!-- 相机权限 -->
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.FLASHLIGHT" />

图像处理的辅助类

另外,ImageUtils类的实现如下:

public class ImageUtils {

    /**
     * 旋转图片
     * @param bitmap
     * @param rotation
     * @Return
     */
    public static Bitmap getRotatedBitmap(Bitmap bitmap, int rotation) {
        Matrix matrix = new Matrix();
        matrix.postRotate(rotation);
        return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                bitmap.getHeight(), matrix, false);
    }

    /**
     * 镜像翻转图片
     * @param bitmap
     * @Return
     */
    public static Bitmap getFlipBitmap(Bitmap bitmap) {
        Matrix matrix = new Matrix();
        matrix.setScale(-1, 1);
        matrix.postTranslate(bitmap.getWidth(), 0);
        return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                bitmap.getHeight(), matrix, false);
    }
}

layout如下:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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="com.cgfay.camerasample.CameraSurfaceViewActivity">

    <FrameLayout
        android:id="@+id/layout_aspect"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </FrameLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_gravity="bottom"
        android:gravity="center">
        <Button
            android:id="@+id/btn_take"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="拍照" />

        <Button
            android:id="@+id/btn_switch"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="切换相机" />
    </LinearLayout>

</FrameLayout>

至此,通过SurfaceView + Camera API 预览拍照功能已经实现。

备注

Camera API 在打开相机是在哪个线程,那么onPreviewFrame回调执行就在哪个线程。

因此,如果要通过onPreviewFrame回调使用预览数据,则可以通过HandlerThread 异步调用Camera进行操作。

另外一个问题,onPreviewFrame方法中不要执行过于复杂的逻辑操作,这

样会阻塞Camera,无法获取新的Frame,导致帧率下降。

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