在Camera2 API中切换闪光灯 [英] Switch flash in Camera2 API

问题描述

我的问题是，当我在不同的闪光模式之间切换然后想要捕获图像时，我的captureBuilder不会设置所选的闪光模式.它仅在我关闭并重新打开相机后才起作用.

My problem is when I switch between different flashmodes and then want to capture an image, my captureBuilder won't set the chosen flashmode. It only works when i close and reopen the camera.

我将 https://github.com/googlesamples/android-Camera2Basic 用作起点.

我的方法:

   private void captureStillPicture() {
  try {
     final Activity activity = (Activity) context;
     if (null == activity || null == mCameraDevice) {
        return;
     }
     // This is the CaptureRequest.Builder that we use to take a picture.
     CaptureRequest.Builder captureBuilder =
           mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
     captureBuilder.addTarget(mImageReader.getSurface());

     // Use the same AE and AF modes as the preview.
     captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
           CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
     setCurrentFlash(captureBuilder);

     // Orientation
     int rotation = activity.getWindowManager()
           .getDefaultDisplay()
           .getRotation();
     captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));

     CameraCaptureSession.CaptureCallback captureCallback =
           new CameraCaptureSession.CaptureCallback() {

              @Override
              public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                    @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
                 super.onCaptureCompleted(session, request, result);
                 Toast.makeText(context, "image captured", Toast.LENGTH_SHORT)
                       .show();
                 unlockFocus();
              }
           };

              mCaptureSession.stopRepeating();
     mCaptureSession.capture(captureBuilder.build(), captureCallback, null);
  } catch (CameraAccessException e) {
     Log.e(this.getClass()
           .getSimpleName(), e.getMessage(), e);
  }

这是setCurrentFlash方法:

This is the setCurrentFlash method:

   private void setCurrentFlash(CaptureRequest.Builder requestBuilder) {
  if (mFlashSupported) {
     switch (flashMode.name()) {
        case FLASH_AUTO:
           requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                 CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
           break;
        case FLASH_ON:
           requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                 CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
           break;
        case FLASH_OFF:
           requestBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF);
           break;
        default:
           requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,
                 CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
           break;
     }
  }

有什么想法，为什么建造者在拍摄前没有正确设置闪光灯?

Any ideas why the builder is not setting the flash correctly before capturing?

***** 编辑 *****

***** EDIT *****

通过调用像Eddy Talvala建议的runPrecaptureSequence()时将闪光灯设置为PreviewRequestBuilder来解决的问题

Solved issue by setting the flash to previewRequestBuilder when calling runPrecaptureSequence() like Eddy Talvala suggested

   private void runPrecaptureSequence() {
  try {
     // This is how to tell the camera to trigger.
     setCurrentFlash(previewRequestBuilder);
     previewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,
           CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);
     // Tell #mCaptureCallback to wait for the precapture sequence to be set.
     state = STATE_WAITING_PRECAPTURE;
     captureSession.capture(previewRequestBuilder.build(), mCaptureCallback, backgroundHandler);
  } catch (CameraAccessException e) {
     e.printStackTrace();
  }

推荐答案

您也想在预览请求中更新Flash模式；通常，在触发预捕获序列(使用AE_PRECAPTURE_TRIGGER)时，摄像头设备希望了解所需的闪光模式，以便知道是否应打开预捕获闪光灯，这需要确定最终的闪光功率.

You want to update the flash mode in your preview request as well; generally the camera device wants to know your desired flash mode when you trigger the precapture sequence (with AE_PRECAPTURE_TRIGGER), so that it knows if it should turn on the precapture flash, which it needs to determine the final flash power.

通常的事件顺序是:

1. 将预览闪光模式设置为所需模式
2. 等待用户按下快门按钮
3. 发出具有预捕获触发器集的单个预览请求(但保留重复的预览请求).
4. 等待AE_STATE_PRECAPTURE在捕获结果中停止成为AE状态
5. 发出最终捕获请求(保持相同的闪光模式)
6. 在ImageReader中获取最终的JPEG

(这忽略了确保聚焦良好，通常在开始预捕获序列之前/同时完成)

(This ignores ensuring focus is good, which generally is done before/in parallel to starting the precapture sequence)

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