Drawing a boundary around some dots in an image

I have recently started working on opencv. I have an image having several dots in a line. I want to make a rectangular border around these dots. I have applied some basic C algorithm but it didn't work for me. This is my code.

int main()

{

    cv::Mat image = imread("C:/Users/Ravi Sharma/Desktop/img.bmp");

     for(int i =0; i < image.rows; i++){
        for(int k = 0; k <image.cols; k ++){
            if((image.at<cv::Vec3b>(k,i)[0] == 0)&&(image.at<cv::Vec3b>(k,i)[1] == 135)&&(image.at<cv::Vec3b>(k,i)[2] == 255))
            {
            (image.at<cv::Vec3b>(k,i)[0] = 0)&&(image.at<cv::Vec3b>(k,i)[1] = 0)&&(image.at<cv::Vec3b>(k,i)[2] = 255);
            }
        }

    }
    imwrite("C:/Users/Ravi Sharma/Desktop/img1.bmp",image);
    cv::namedWindow("Window1");
    cv::imshow("Window1",image);
    cv::waitKey(50000);
    return 1;
} 

This code is not updating the pixel value. Please help me correcting the code to get the desired result. How I can use cvminmaxloc function to do the same. Thanx in advance.