public class FotografiaActivity extends AppCompatActivity {
    EditText etUsuario, etNservicio;
    private static String APP_DIRECTORY = "MyPictureApp/";
    private static String MEDIA_DIRECTORY = APP_DIRECTORY + "PictureApp";

    private final int MY_PERMISSIONS = 100;
    private final int PHOTO_CODE = 200;
    private final int SELECT_PICTURE = 300;

    private ImageView mSetImage;
    private Button mOptionButton;
    private RelativeLayout mRlView;

    private String mPath;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fotografia);
        etUsuario=(EditText)findViewById(R.id.etUsuario);
        etNservicio=(EditText)findViewById(R.id.etNservicio);
        mSetImage = (ImageView) findViewById(R.id.set_picture);
        mOptionButton = (Button) findViewById(R.id.show_options_button);
        mRlView = (RelativeLayout) findViewById(R.id.rl_view);

        Bundle extras = getIntent().getExtras();
        String dato= extras.getString("Usuarios").toString();
        etUsuario.setText(dato);
        String datos= extras.getString("Nservicio").toString();
        etNservicio.setText(datos);
        if(mayRequestStoragePermission())
            mOptionButton.setEnabled(true);
        else
            mOptionButton.setEnabled(false);


        mOptionButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showOptions();
            }
        });

    }
    public void checkCancelar(View arg0){
        Intent intent = new Intent(FotografiaActivity.this,DashboardActivity.class);
        Bundle extras = new Bundle();
        extras.putString("Usuarios",etUsuario.getText().toString());
        intent.putExtras(extras);
        startActivity(intent);
        FotografiaActivity.this.finish();
    }
    public void checkFinalizar(View arg0){
        Intent intent = new Intent(FotografiaActivity.this,UbicacionActivity.class);
        Bundle extras = new Bundle();
        extras.putString("Usuarios",etUsuario.getText().toString());
        extras.putString("Nservicio", etNservicio.getText().toString());
        intent.putExtras(extras);
        startActivity(intent);
        FotografiaActivity.this.finish();
    }
    private boolean mayRequestStoragePermission() {

        if(Build.VERSION.SDK_INT < Build.VERSION_CODES.M)
            return true;

        if((checkSelfPermission(WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) &&
                (checkSelfPermission(CAMERA) == PackageManager.PERMISSION_GRANTED))
            return true;

        if((shouldShowRequestPermissionRationale(WRITE_EXTERNAL_STORAGE)) || (shouldShowRequestPermissionRationale(CAMERA))){
            Snackbar.make(mRlView, "Los permisos son necesarios para poder usar la aplicación",
                    Snackbar.LENGTH_INDEFINITE).setAction(android.R.string.ok, new View.OnClickListener() {
                @TargetApi(Build.VERSION_CODES.M)
                @Override
                public void onClick(View v) {
                    requestPermissions(new String[]{WRITE_EXTERNAL_STORAGE, CAMERA}, MY_PERMISSIONS);
                }
            });
        }else{
            requestPermissions(new String[]{WRITE_EXTERNAL_STORAGE, CAMERA}, MY_PERMISSIONS);
        }

        return false;
    }

    private void showOptions() {
        final CharSequence[] option = {"Tomar foto", "Elegir de galeria", "Cancelar"};
        final AlertDialog.Builder builder = new AlertDialog.Builder(FotografiaActivity.this);
        builder.setTitle("Eleige una opción");
        builder.setItems(option, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                if(option[which] == "Tomar foto"){
                    openCamera();
                }else if(option[which] == "Elegir de galeria"){
                    Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                    intent.setType("image/*");
                    startActivityForResult(Intent.createChooser(intent, "Selecciona app de imagen"), SELECT_PICTURE);
                }else {
                    dialog.dismiss();
                }
            }
        });

        builder.show();
    }

    private void openCamera() {
        File file = new File(Environment.getExternalStorageDirectory(), MEDIA_DIRECTORY);
        boolean isDirectoryCreated = file.exists();

        if(!isDirectoryCreated)
            isDirectoryCreated = file.mkdirs();

        if(isDirectoryCreated){
            Long timestamp = System.currentTimeMillis() / 1000;
            String imageName = timestamp.toString() + ".jpg";

            mPath = Environment.getExternalStorageDirectory() + File.separator + MEDIA_DIRECTORY
                    + File.separator + imageName;

            File newFile = new File(mPath);

            Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
            intent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(newFile));
            startActivityForResult(intent, PHOTO_CODE);
        }
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("file_path", mPath);
    }

    @Override
    protected void onRestoreInstanceState(Bundle savedInstanceState) {
        super.onRestoreInstanceState(savedInstanceState);

        mPath = savedInstanceState.getString("file_path");
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if(resultCode == RESULT_OK){
            switch (requestCode){
                case PHOTO_CODE:
                    MediaScannerConnection.scanFile(this,
                            new String[]{mPath}, null,
                            new MediaScannerConnection.OnScanCompletedListener() {
                                @Override
                                public void onScanCompleted(String path, Uri uri) {
                                    Log.i("ExternalStorage", "Scanned " + path + ":");
                                    Log.i("ExternalStorage", "-> Uri = " + uri);
                                }
                            });


                    Bitmap bitmap = BitmapFactory.decodeFile(mPath);
                    mSetImage.setImageBitmap(bitmap);
                    break;
                case SELECT_PICTURE:
                    Uri path = data.getData();
                    mSetImage.setImageURI(path);
                    break;

            }
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if(requestCode == MY_PERMISSIONS){
            if(grantResults.length == 2 && grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED){
                Toast.makeText(FotografiaActivity.this, "Permisos aceptados", Toast.LENGTH_SHORT).show();
                mOptionButton.setEnabled(true);
            }
        }else{
            showExplanation();
        }
    }

    private void showExplanation() {
        AlertDialog.Builder builder = new AlertDialog.Builder(FotografiaActivity.this);
        builder.setTitle("Permisos denegados");
        builder.setMessage("Para usar las funciones de la app necesitas aceptar los permisos");
        builder.setPositiveButton("Aceptar", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                Intent intent = new Intent();
                intent.setAction(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
                Uri uri = Uri.fromParts("package", getPackageName(), null);
                intent.setData(uri);
                startActivity(intent);
            }
        });
        builder.setNegativeButton("Cancelar", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                finish();
            }
        });

        builder.show();
    }
}

Bitmap bm = BitmapFactory.decodeFile("/path/to/image.jpg");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.JPEG, 100, baos); //bm = Bitmap
byte[] b = baos.toByteArray();

String encodedImage = Base64.encodeToString(byteArrayImage, Base64.DEFAULT);

file_put_contents('img.png', base64_decode($_POST['imagen_base64']));