不知道干嘛的

cv::Vec3b getColorSubpix(const cv::Mat& img, cv::Point2f pt);
cv::Vec3b getColorSubpix1(const cv::Mat& img, cv::Point2f pt)
{
	cv::Mat patch;
	cv::getRectSubPix(img, cv::Size(1, 1), pt, patch);
	return patch.at(0, 0);
}
int main()
{

	Mat img = imread("C:\\Users\\BZL\\Desktop\\lena.jpg");
	Point2f center(img.cols / 2-100, img.rows / 2-100);
	std::cout << getColorSubpix(img, center);
	std::cout << getColorSubpix1(img, center);
	return 0;
}

cv::Vec3b getColorSubpix(const cv::Mat& img, cv::Point2f pt)
{
	assert(!img.empty());
	assert(img.channels() == 3);

	int x = (int)pt.x;
	int y = (int)pt.y;

	int x0 = cv::borderInterpolate(x, img.cols, cv::BORDER_REFLECT_101);
	int x1 = cv::borderInterpolate(x + 1, img.cols, cv::BORDER_REFLECT_101);
	int y0 = cv::borderInterpolate(y, img.rows, cv::BORDER_REFLECT_101);
	int y1 = cv::borderInterpolate(y + 1, img.rows, cv::BORDER_REFLECT_101);

	float a = pt.x - (float)x;
	float c = pt.y - (float)y;

	uchar b = (uchar)cvRound((img.at(y0, x0)[0] * (1.f - a) + img.at(y0, x1)[0] * a) * (1.f - c)
		+ (img.at(y1, x0)[0] * (1.f - a) + img.at(y1, x1)[0] * a) * c);
	uchar g = (uchar)cvRound((img.at(y0, x0)[1] * (1.f - a) + img.at(y0, x1)[1] * a) * (1.f - c)
		+ (img.at(y1, x0)[1] * (1.f - a) + img.at(y1, x1)[1] * a) * c);
	uchar r = (uchar)cvRound((img.at(y0, x0)[2] * (1.f - a) + img.at(y0, x1)[2] * a) * (1.f - c)
		+ (img.at(y1, x0)[2] * (1.f - a) + img.at(y1, x1)[2] * a) * c);

	return cv::Vec3b(b, g, r);
}