Opencv android, capture image

久未见 提交于 2019-12-12 08:17:24

问题


I will try to simplify my problem. Lets say i just want to see grayscale images using camera, i do it this way:

public Mat onCameraFrame(CvCameraViewFrame inputFrame) {

return inputFrame.gray();

 }

And this works just fine, i can now dinamically see grey image on my screen. But problem is when i try to capture this image (frame). Instead of capturing it in grey, it captures it in color (it ignores all the effects i do in onCameraFrame). To capture image i use the same way done in Tutorial 3 - Camera Control (Here is relevant code):

public class MainActivity extends Activity implements CvCameraViewListener2, View.OnTouchListener {

private CameraLab mOpenCvCameraView;

protected void onCreate(Bundle savedInstanceState) {

     mOpenCvCameraView = (CameraLab) findViewById(R.id.openCVCamera);
        mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);
}

@Override
    public boolean onTouch(View v, MotionEvent event) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss");
        String currentDateandTime = sdf.format(new Date());
        String fileName = "Image_"+currentDateandTime + ".jpg";
        mOpenCvCameraView.takePicture(fileName);
        return false;
    }
}


public class CameraLab extends JavaCameraView implements PictureCallback {

private String mPictureFileName;

public void takePicture(final String fileName) {
        Log.i(TAG, "Taking picture");

        this.mPictureFileName = fileName;

        mCamera.setPreviewCallback(null);

        // PictureCallback is implemented by the current class
        mCamera.takePicture(null, null, this);
    }

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        Log.i(TAG, "Saving a bitmap to file");
        mCamera.startPreview();
        mCamera.setPreviewCallback(this);

        // Write the image in a file (in jpeg format)
       try {
            FileOutputStream fos = new FileOutputStream(mPictureFileName);

            fos.write(data);
            fos.close();

        } catch (java.io.IOException e) {
            Log.e("PictureDemo", "Exception in photoCallback", e);
        }

    }
}

So, to recap, problem is whatever i do in onCameraFrame (make image grey, detect circles...) when i capture image i dont get any of those effects, i just get a normal image.

How can i fix this ?


回答1:


It is because you are modifying Mat in onCameraFrame() and writing the image data to file in onPictureTaken().

The Mat in onCameraFrame is never written to the file.

The byte[] in onPictureTaken() contains the picture taken by the camera when you push a button or touch on the screen whatever is triggering takePicture().

If you want to the write picture with some effects then you will have to convert byte[] to Mat and then make effects in this Mat and then write it to file using imwrite() or convert the modified Mat back to byte[] and then write it to file using FileOutputStream as shown in your code.

imwrite() will be slower than the FileOutputStream approach




回答2:


This is super duper old but I saw it so many times while searching. I solved my issue by using

Imgcodecs.imwrite(fileName,mRgba);

instead of

javaCameraView.takePicture(fileName);

in my onTouch method.



来源:https://stackoverflow.com/questions/30103036/opencv-android-capture-image

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