How to adjust Image brightness Using OpenCV effectively in android studio

I am using below code to adjust image brightness using OpenCv but the Image gets all white or all black. here is my code used in a seek bar progress change. if I slide seek bar to 50 the image get brighter 50 percent. when I slide back to 0 the brighter Image is processed not original given.

function

 //BRIGHTNESS
    public Bitmap Brightness(Bitmap bitmap, double value){
        Mat src = new Mat(bitmap.getHeight(),bitmap.getWidth(), CvType.CV_8UC1);
        Utils.bitmapToMat(bitmap,src);
        src.convertTo(src,-1,1,value);
        Bitmap result = Bitmap.createBitmap(src.cols(),src.rows(), Bitmap.Config.ARGB_8888);
        Utils.matToBitmap(src,result);
        return result;
    }