public static boolean isDark(Bitmap bitmap){
        boolean dark=false;

        float darkThreshold = bitmap.getWidth()*bitmap.getHeight()*0.45f;
        int darkPixels=0;

        int[] pixels = new int[bitmap.getWidth()*bitmap.getHeight()];
        bitmap.getPixels(pixels,0,bitmap.getWidth(),0,0,bitmap.getWidth(),bitmap.getHeight());

        for(int pixel : pixels){
            int color = pixels[i];
            int r = Color.red(color);
            int g = Color.green(color);
            int b = Color.blue(color);
            double luminance = (0.299*r+0.0f + 0.587*g+0.0f + 0.114*b+0.0f);
            if (luminance<150) {
                darkPixels++;
            }
        }

        if (darkPixels >= darkThreshold) {
            dark = true;
        }
        long duration = System.currentTimeMillis()-s;
        return dark;
    }