Apply some Filters to an image of car using Open CV C++

Question

am trying to apply some pre process functions to the image of cars for my graduation project License plate recognition but i face an issue the picture looks poor

The Orignial image enter image description here

1- Convert to Grayscale.

2- Gaussian Blur with 3x3 or 5x5 filter.

3- Apply Sobel Filter to find vertical edges.

4- Threshold the resultant image to get a binary image.

5- Apply a morphological close operation using suitable structuring element. enter image description here

Question is

How can i optimize the picture to be able to get perfect result in the next steps

private: System::Void btnProcess_Click(System::Object^  sender, System::EventArgs^  e) {

cv::Mat imgOriginalScene;
cv::Mat imgGrayscale;
cv::Mat imgGaussianBlur;
cv::Mat imgCannyEdgeDetection;
cv::Mat imgMorphologyEx;

cv::Mat imgScaled;
cv::Mat imgPlate;
cv::Mat imgAbove;
cv::Mat imgThresh;

if (file_path_temp != nullptr)
{
    IntPtr pointer_temp = Marshal::StringToHGlobalAnsi(file_path_temp);
    const char* input_location = static_cast<const char*>(pointer_temp.ToPointer());
    imgOriginalScene = cv::imread(input_location, CV_LOAD_IMAGE_ANYDEPTH | CV_LOAD_IMAGE_ANYCOLOR);

    Marshal::FreeHGlobal(pointer_temp);


    if (!imgOriginalScene.empty())
    {
        // first step convert the image to the Gray scale image
        cv::cvtColor(imgOriginalScene, imgGrayscale, CV_BGR2GRAY);

        // apply Guassin Blur with 3x3 or 5x5
        cv::GaussianBlur(imgGrayscale, imgGaussianBlur, cv::Size(3,3),0 );
        
        // apply the threshold 
        cv::adaptiveThreshold(imgGaussianBlur, imgThresh, 255.0, CV_ADAPTIVE_THRESH_GAUSSIAN_C, CV_THRESH_BINARY_INV, 19, 9);

        // apply Canny edge detection
        cv::Canny(imgThresh, imgCannyEdgeDetection, 35, 90);

        cv::Mat structuringElement = cv::getStructuringElement(cv::MORPH_ELLIPSE, cv::Size(3, 3));
        cv::morphologyEx(imgCannyEdgeDetection, imgMorphologyEx, cv::MORPH_CLOSE, structuringElement);

        cv::imwrite("temp/temp.bmp", imgMorphologyEx);
        System::Drawing::Graphics^ graphics = PicBoxCar->CreateGraphics();
        System::Drawing::Bitmap^ b = gcnew System::Drawing::Bitmap("temp/temp.bmp");
        System::Drawing::RectangleF rect(0, 0, (float)PicBoxCar->Width, (float)PicBoxCar->Height);
        graphics->DrawImage(b, rect);
        delete b;
    }
}
else {
        MessageBox::Show("Cannot open this image please choose another one !!", "Path:");

}