拍照

拍照是相机的最重要功能之一，拍照模块基于相机复杂的逻辑，为了保证用户拍出的照片质量，在中间步骤可以设置分辨率、闪光灯、焦距、照片质量及旋转角度等信息。

开发步骤

详细的API说明请参考Camera API参考。

导入image接口。创建拍照输出流的SurfaceId以及拍照输出的数据，都需要用到系统提供的image接口能力，导入image接口的方法如下。
```
import image from '@ohos.multimedia.image';
import camera from '@ohos.multimedia.camera';
import { BusinessError } from '@ohos.base';
```

获取SurfaceId。

通过image的createImageReceiver方法创建ImageReceiver实例，再通过实例的getReceivingSurfaceId方法获取SurfaceId，与拍照输出流相关联，获取拍照输出流的数据。

async function getImageReceiverSurfaceId(): Promise<string|undefined> {
  let photoSurfaceId: string|undefined = undefined;
  let receiver: image.ImageReceiver = image.createImageReceiver(640, 480, 4, 8);
  console.info('before ImageReceiver check');
  if (receiver !== undefined) {
    console.info('ImageReceiver is ok');
    photoSurfaceId = await receiver.getReceivingSurfaceId();
    console.info(`ImageReceived id: ${JSON.stringify(photoSurfaceId)}`);
  } else {
    console.info('ImageReceiver is not ok');
  }
  return photoSurfaceId;
}

创建拍照输出流。

通过CameraOutputCapability类中的photoProfiles()方法，可获取当前设备支持的拍照输出流，通过createPhotoOutput()方法传入支持的某一个输出流及步骤一获取的SurfaceId创建拍照输出流。

function getPhotoOutput(cameraManager: camera.CameraManager, cameraOutputCapability: camera.CameraOutputCapability, photoSurfaceId: string): camera.PhotoOutput|undefined {
  let photoProfilesArray: Array<camera.Profile> = cameraOutputCapability.photoProfiles;
  if (!photoProfilesArray) {
    console.error("createOutput photoProfilesArray == null||undefined");
  }
  let photoOutput: camera.PhotoOutput|undefined = undefined;
  try {
    photoOutput = cameraManager.createPhotoOutput(photoProfilesArray[0], photoSurfaceId);
  } catch (error) {
    let err = error as BusinessError;
    console.error(`Failed to createPhotoOutput. error: ${JSON.stringify(err)}`);
  }
  return photoOutput;
}

参数配置。

配置相机的参数可以调整拍照的一些功能，包括闪光灯、变焦、焦距等。

function configuringSession(captureSession: camera.CaptureSession): void {
  // 判断设备是否支持闪光灯
  let flashStatus: boolean = false;
  try {
    flashStatus = captureSession.hasFlash();
  } catch (error) {
    let err = error as BusinessError;
    console.error(`Failed to hasFlash. error: ${JSON.stringify(err)}`);
  }
  console.info(`Promise returned with the flash light support status: ${flashStatus}`);
  if (flashStatus) {
    // 判断是否支持自动闪光灯模式
    let flashModeStatus: boolean = false;
    try {
      let status: boolean = captureSession.isFlashModeSupported(camera.FlashMode.FLASH_MODE_AUTO);
      flashModeStatus = status;
    } catch (error) {
      let err = error as BusinessError;
      console.error(`Failed to check whether the flash mode is supported. error: ${JSON.stringify(err)}`);
    }
    if (flashModeStatus) {
      // 设置自动闪光灯模式
      try {
        captureSession.setFlashMode(camera.FlashMode.FLASH_MODE_AUTO);
      } catch (error) {
        let err = error as BusinessError;
        console.error(`Failed to set the flash mode. error: ${JSON.stringify(err)}`);
      }
    }
  }
  // 判断是否支持连续自动变焦模式
  let focusModeStatus: boolean = false;
  try {
    let status: boolean = captureSession.isFocusModeSupported(camera.FocusMode.FOCUS_MODE_CONTINUOUS_AUTO);
    focusModeStatus = status;
  } catch (error) {
    let err = error as BusinessError;
    console.error(`Failed to check whether the focus mode is supported. error: ${JSON.stringify(err)}`);
  }
  if (focusModeStatus) {
    // 设置连续自动变焦模式
    try {
      captureSession.setFocusMode(camera.FocusMode.FOCUS_MODE_CONTINUOUS_AUTO);
    } catch (error) {
      let err = error as BusinessError;
      console.error(`Failed to set the focus mode. error: ${JSON.stringify(err)}`);
    }
  }
  // 获取相机支持的可变焦距比范围
  let zoomRatioRange: Array<number> = [];
  try {
    zoomRatioRange = captureSession.getZoomRatioRange();
  } catch (error) {
    let err = error as BusinessError;
    console.error(`Failed to get the zoom ratio range. error: ${JSON.stringify(err)}`);
  }
  if (zoomRatioRange.length <= 0 ) {
    return;
  }
  // 设置可变焦距比
  try {
    captureSession.setZoomRatio(zoomRatioRange[0]);
  } catch (error) {
    let err = error as BusinessError;
    console.error(`Failed to set the zoom ratio value. error: ${JSON.stringify(err)}`);
  }
}

触发拍照。

通过photoOutput类的capture()方法，执行拍照任务。该方法有两个参数，第一个参数为拍照设置参数的setting，setting中可以设置照片的质量和旋转角度，第二参数为回调函数。

function capture(captureLocation: camera.Location, photoOutput: camera.PhotoOutput): void {
  let settings: camera.PhotoCaptureSetting = {
    quality: camera.QualityLevel.QUALITY_LEVEL_HIGH,  // 设置图片质量高
    rotation: camera.ImageRotation.ROTATION_0,  // 设置图片旋转角度0
    location: captureLocation,  // 设置图片地理位置
    mirror: false  // 设置镜像使能开关(默认关)
  };
  photoOutput.capture(settings, (err: BusinessError) => {
    if (err) {
      console.error(`Failed to capture the photo. error: ${JSON.stringify(err)}`);
      return;
    }
    console.info('Callback invoked to indicate the photo capture request success.');
  });
}

状态监听

在相机应用开发过程中，可以随时监听拍照输出流状态，包括拍照流开始、拍照帧的开始与结束、拍照输出流的错误。

通过注册固定的captureStart回调函数获取监听拍照开始结果，photoOutput创建成功时即可监听，拍照第一次曝光时触发，该事件返回此次拍照的captureId。

function onPhotoOutputCaptureStart(photoOutput: camera.PhotoOutput): void {
  photoOutput.on('captureStart', (err: BusinessError, captureId: number) => {
    console.info(`photo capture stated, captureId : ${captureId}`);
  });
}

通过注册固定的captureEnd回调函数获取监听拍照结束结果，photoOutput创建成功时即可监听，该事件返回结果为拍照完全结束后的相关信息CaptureEndInfo。

function onPhotoOutputCaptureEnd(photoOutput: camera.PhotoOutput): void {
  photoOutput.on('captureEnd', (err: BusinessError, captureEndInfo: camera.CaptureEndInfo) => {
    console.info(`photo capture end, captureId : ${captureEndInfo.captureId}`);
    console.info(`frameCount : ${captureEndInfo.frameCount}`);
  });
}

通过注册固定的error回调函数获取监听拍照输出流的错误结果。callback返回拍照输出接口使用错误时的对应错误码，错误码类型参见CameraErrorCode。

function onPhotoOutputError(photoOutput: camera.PhotoOutput): void {
  photoOutput.on('error', (error: BusinessError) => {
    console.info(`Photo output error code: ${error.code}`);
  });
}