cvtColor(src, src_gray, CV_BGR2GRAY)报错

利用cvtColor 进行灰度转换时，不能将  灰度图 转为灰度图，所以在转换前，需对原始图像进行判断。

将这个改成以下

int main(int argc, char* argv[])
{
	Mat m = imread("2.jpg", CV_LOAD_IMAGE_COLOR);
	IplImage src(m);
	cvNamedWindow("showImage");
	IplImage* gimg = cvCreateImage(cvGetSize(&src), 8, 1);
	cvCvtColor(&src, gimg, CV_BGR2GRAY);
	cvSaveImage("1.jpg", gimg);
	cvShowImage("showImage", gimg);
	cvWaitKey(0);
	cvReleaseImage(&gimg);
	cvDestroyWindow("showImage");
	return 0;
}

　　完整代码：

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>
#include <stdio.h>
#include <stdlib.h>

using namespace cv;
using namespace std;

/// Global variables
Mat src, src_gray;
int thresh = 200;
int max_thresh = 255;

char* source_window = "Source image";
char* corners_window = "Corners detected";

/// Function header
void cornerHarris_demo(int, void*);
void cvtColor_src(Mat &src, Mat &dst);

/** @function main */
int main(int argc, char** argv)
{
	/// Load source image and convert it to gray
	src = imread("E:\\VS2015Opencv\\vs2015\\project\\picture\\06.jpg");

	
	//  转换单通道
	cvtColor_src(src,src_gray);


	/// Create a window and a trackbar
	namedWindow(source_window, CV_WINDOW_AUTOSIZE);
	createTrackbar("Threshold: ", source_window, &thresh, max_thresh, cornerHarris_demo);
	imshow(source_window, src);

	cornerHarris_demo(0, 0);

	waitKey(0);
	return(0);
}

void cvtColor_src(Mat &src, Mat &src_gray)
{
	//  转换单通道
	if (src.channels() == 4) {
		cv::cvtColor(src, src_gray, CV_BGRA2GRAY);
	}
	else if (src.channels() == 3) {
		cv::cvtColor(src, src_gray, CV_BGR2GRAY);
	}
	else if (src.channels() == 2) {
		cv::cvtColor(src, src_gray, CV_BGR5652GRAY);
	}
	else if (src.channels() == 1) {// 单通道的图片直接就不需要处理
		src_gray = src;
	}
	else { // 负数,说明图有问题 直接返回	
		src_gray = src;
	}

}

/** @function cornerHarris_demo */
void cornerHarris_demo(int, void*)
{

	Mat dst, dst_norm, dst_norm_scaled;
	dst = Mat::zeros(src.size(), CV_32FC1);

	/// Detector parameters
	int blockSize = 2;
	int apertureSize = 3;
	double k = 0.04;

	/// Detecting corners
	cornerHarris(src_gray, dst, blockSize, apertureSize, k, BORDER_DEFAULT);

	/// Normalizing
	normalize(dst, dst_norm, 0, 255, NORM_MINMAX, CV_32FC1, Mat());
	convertScaleAbs(dst_norm, dst_norm_scaled);

	/// Drawing a circle around corners
	for (int j = 0; j < dst_norm.rows; j++)
	{
		for (int i = 0; i < dst_norm.cols; i++)
		{
			if ((int)dst_norm.at<float>(j, i) > thresh)
			{
				circle(dst_norm_scaled, Point(i, j), 5, Scalar(0), 2, 8, 0);
			}
		}
	}
	/// Showing the result
	namedWindow(corners_window, CV_WINDOW_AUTOSIZE);
	imshow(corners_window, dst_norm_scaled);
}