Ios Image Convert in Grayscale with document Type by OPENCV framework

please help me my question is same as this link Open CV image effects I can't able to understand how to call this function from code Here is answer from link above:

#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <cstdlib>

int
main(int argc, char **argv)
{

  cv::Mat image = cv::imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE);
  assert(!image.empty());

  cv::Mat binary;
  cv::adaptiveThreshold(image, binary, 255, CV_ADAPTIVE_THRESH_MEAN_C, CV_THRESH_BINARY, 5, 7);

  cv::imshow("Orig", image);
  cv::imshow("Binary", binary);
  cv::waitKey(0);
  cv::imwrite("binary.png", binary);

  return EXIT_SUCCESS;

}

Here is my code this is working my code convert in grayscale but i am confuse how to use this function int main(int argc, char **argv)

- (IBAction)secondbutton:(id)sender
{

    [self cvMatGrayFromUIImage:imageView.image];

}
- (cv::Mat)cvMatGrayFromUIImage:(UIImage *)image_get
{
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(image_get.CGImage);
    CGFloat cols = image_get.size.width;
    CGFloat rows = image_get.size.height;

    cv::Mat cvMat(rows, cols, CV_8UC1); // 8 bits per component, 1 channels

    CGContextRef contextRef = CGBitmapContextCreate(cvMat.data,                 // Pointer to data
                                                    cols,                       // Width of bitmap
                                                    rows,                       // Height of bitmap
                                                    8,                          // Bits per component
                                                    cvMat.step[0],              // Bytes per row
                                                    colorSpace,                 // Colorspace
                                                    kCGImageAlphaNoneSkipLast |
                                                    kCGBitmapByteOrderDefault); // Bitmap info flags

    CGContextDrawImage(contextRef, CGRectMake(0, 0, cols, rows), image.CGImage);
    CGContextRelease(contextRef);
     [self UIImageFromCVMat:cvMat];
    return cvMat;
 }
-(UIImage *)UIImageFromCVMat:(cv::Mat)cvMat
{
    NSData *data = [NSData dataWithBytes:cvMat.data length:cvMat.elemSize()*cvMat.total()];
    CGColorSpaceRef colorSpace;

    if (cvMat.elemSize() == 1) {
        colorSpace = CGColorSpaceCreateDeviceGray();
    } else {
        colorSpace = CGColorSpaceCreateDeviceRGB();
    }

    CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);

    // Creating CGImage from cv::Mat
    CGImageRef imageRef = CGImageCreate(cvMat.cols,                                 //width
                                        cvMat.rows,                                 //height
                                        8,                                          //bits per component
                                        8 * cvMat.elemSize(),                       //bits per pixel
                                        cvMat.step[0],                            //bytesPerRow
                                        colorSpace,                                 //colorspace
                                        kCGImageAlphaNone|kCGBitmapByteOrderDefault,// bitmap info
                                        provider,                                   //CGDataProviderRef
                                        NULL,                                       //decode
                                        false,                                      //should interpolate
                                        kCGRenderingIntentDefault                   //intent
                                        );


    // Getting UIImage from CGImage
    UIImage *finalImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGDataProviderRelease(provider);
    CGColorSpaceRelease(colorSpace);
    imageView.image=finalImage;

    return finalImage;
}