问OpenCV返回黑白图像而不是灰度

EN

cv::Mat maskCrop(std::string imageName, std::string maskName)
{
    cv::Mat image,mask;
    image = cv::imread( imageName, CV_LOAD_IMAGE_GRAYSCALE);
    mask = cv::imread( maskName,CV_LOAD_IMAGE_GRAYSCALE);
    cv::Mat final_image;
    cv::resize(image, image, mask.size());  // make the size of mask and image same
    
    cv::bitwise_and(image, mask, final_image); //Apply mask
    
    // define rectangular window for cropping
    int offset_x = 1250;  // top left corner, for cropping
    int offset_y = 1550;
    
    cv::Rect roi;
    roi.x = offset_x;
    roi.y = offset_y;
    roi.width = 550;
    roi.height = 650;
    
    // Crop the original image to the defined ROI //
    
    cv::Mat crop = final_image(roi);
   //scale the image
    float beta = 1.0 / 255.0;
    crop *=beta;  // divide the max pixel vaue i.e. 255
    
    //Examinig whether scaling can be undone !!!!
    cv::imwrite("/home/dpk/Desktop/ip-rings/gray_image.jpg",crop*255);
    
    return crop;
}