void calcHist(const Mat* images, int nimages,
		const int* channels, InputArray mask,
		OutputArray hist, int dims, const int* histSize,
		const float** ranges, bool uniform = true, bool accumulate = false);

	Mat img;
	img = imread("貓1.jpg",0);
	int channels[] = { 0 };
	int bins = 256;
	Mat hist;
	int hist_size[] = { bins };
	float range[] = { 0,256 };
	const float*ranges[] = { range };
	calcHist(&img, 1, 0, Mat(), hist, 1, hist_size, ranges);
	double max_val;
	minMaxLoc(hist, 0, &max_val);//定義矩陣中最小值，最大值的位置
	int scale = 2;
	int hist_height =256;
	Mat hist_ing = Mat::zeros(hist_height, scale*bins, CV_8UC3);
	for (int i = 0; i < bins; i++)
	{
		float bin_val = hist.at<float>(i);//圖像的灰度頻率表
		int inten = cvRound(bin_val*hist_height / max_val);//繪制高度
		rectangle(hist_ing, Point(scale*i, hist_height - 1), Point((i + 1)*scale - 1, hist_height - inten), CV_RGB(255, 255, 255));
	}
	imshow("直方圖", hist_ing);
	waitKey(0);