Camera Preview is too dark in low light android

问题

My camera app preview is too dark in low light. If I open my google camera it will increase brightness inside the preview so that our face is visible to take photos. But my preview is completely dark. I have handled the brightness and lightsensor. My Lightsensor works when is some light. I need to make preview is visible. Let me what should I have to handle?

 public void initialBrightness() {
        try {
            brightnessMode = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE);
        } catch (Settings.SettingNotFoundException e) {
            e.printStackTrace();
        }
        if (brightnessMode == Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC) {
            Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE,
                    Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL);
            brightnessModeAuto = true;
        }
        Settings.System.putInt(this.getContentResolver(), Settings.System.SCREEN_BRIGHTNESS, 95);
        WindowManager.LayoutParams lp = getWindow().getAttributes();
        lp.screenBrightness = 100;
        getWindow().setAttributes(lp);

    }

I'm calling this method in onCreate method before camera preview class is called.

回答1:

To solve the problem you have to unlock autoExposureCompensation and set to the MAX value:

Camera.Parameters params = mCamera.getParameters();

params.setExposureCompensation(params.getMaxExposureCompensation());

if(params.isAutoExposureLockSupported()) {
 params.setAutoExposureLock(false);
}

mCamera.setParameters(params);

According to Android Develop > Reference > Camera.Parameters

Changing the white balance mode with setWhiteBalance(String) will release the auto-white balance lock if it is set.

Exposure compensation, AE lock, and AWB lock can be used to capture an exposure-bracketed burst of images, for example. Auto-white balance state, including the lock state, will not be maintained after camera release() is called.

Locking auto-white balance after open() but before the first call to startPreview() will not allow the auto-white balance routine to run at all, and may result in severely incorrect color in captured images.

So be careful and use the mentioned code after the first call to startPreview()

回答2:

Try the below code. It worked for me.

   previewRequestBuilder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE, getRange());//This line of code is used for adjusting the fps range and fixing the dark preview
   previewRequestBuilder.set(CaptureRequest.CONTROL_AE_LOCK, false);
   previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);

getRange() function as belw:

private Range<Integer> getRange() {
    CameraManager mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    CameraCharacteristics chars = null;
    try {
        chars = mCameraManager.getCameraCharacteristics(cameraId);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
    Range<Integer>[] ranges = chars.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES);

    Range<Integer> result = null;

    for (Range<Integer> range : ranges) {
        int upper = range.getUpper();

        // 10 - min range upper for my needs
        if (upper >= 10) {
            if (result == null || upper < result.getUpper().intValue()) {
                result = range;
            }
        }
    }
    return result;
}

回答3:

What worked for me, after hours of testing with different settings was to reduce Frames per Second.

By doing so I guess the Automatic Exposure correction has enough time to compute the best settings for the available light.

So, reducing from 30 fps to 10 fps made it.

mCameraSource = new CameraSource.Builder(context, detector)
            .setRequestedPreviewSize(640, 480)
            .setFacing(CameraSource.CAMERA_FACING_FRONT)
            .setRequestedFps(10.0f)
            .build();

回答4:

From my experiments, scene-mode setting can change the preview (unlike ISO or exposure-compensation, which both work for captured pictures). Don't use auto. Try scene-mode-values=night or scene-mode=dusk-dawn.

The problem with scenes is that the supported values are not standardized across devices. But some kind of night is usually present.

回答5:

By reading the open source code of Android Camera app here:

https://android.googlesource.com/platform/packages/apps/Camera.git/+/lollipop-release

It initialize the camera this way:

// Reset preview frame rate to the maximum because it may be lowered by
// video camera application.
 List<Integer> frameRates = parameters.getSupportedPreviewFrameRates();
        if (frameRates != null) {
            Integer max = Collections.max(frameRates);
            parameters.setPreviewFrameRate(max);
        }

And it works well in Android Nexus 5, lollipop.

来源：https://stackoverflow.com/questions/28429071/camera-preview-is-too-dark-in-low-light-android

标签

android

android-camera

preview