如何在OpenCv中将cv :: Mat转换为灰度？ [英] How can I convert a cv::Mat to a gray scale in OpenCv?

问题描述

如何将cv :: Mat转换为灰度？

How can I convert a cv::Mat to a gray scale?

我试图从opencv运行drawKeyPoints func，但是我一直得到一个Assertion Filed错误。我猜想它需要在参数中接收灰度图像而不是彩色图像。

I am trying to run drawKeyPoints func from opencv, however I have been getting an Assertion Filed error. My guess is that it needs to receive a gray scale image rather than a color image in the parameter.

void SurfDetector(cv::Mat img){
vector<cv::KeyPoint> keypoints;
cv::Mat featureImage;

cv::drawKeypoints(img, keypoints, featureImage, cv::Scalar(255,255,255) ,cv::DrawMatchesFlags::DRAW_RICH_KEYPOINTS);

cv::namedWindow("Picture");
cv::imshow("Picture", featureImage);

}

推荐答案

使用C ++ API，函数名稍有改变，现在写入：

Using the C++ API, the function name has slightly changed and it writes now:

#include <opencv2/imgproc/imgproc.hpp>

cv::Mat greyMat, colorMat;
cv::cvtColor(colorMat, greyMat, CV_BGR2GRAY);

主要的困难是函数在 imgproc 在核心），默认情况下，cv :: Mat是蓝绿红（BGR）顺序，而不是更常见的RGB。

The main difficulties are that the function is in the imgproc module (not in the core), and by default cv::Mat are in the Blue Green Red (BGR) order instead of the more common RGB.

OpenCV 3

从OpenCV 3.0开始，还有另一个约定。
转换代码嵌入在命名空间 cv :: 中，并以 COLOR 为前缀。
所以，示例变为：

Starting with OpenCV 3.0, there is yet another convention. Conversion codes are embedded in the namespace cv:: and are prefixed with COLOR. So, the example becomes then:

#include <opencv2/imgproc/imgproc.hpp>

cv::Mat greyMat, colorMat;
cv::cvtColor(colorMat, greyMat, cv::COLOR_BGR2GRAY);

据我所见，包含的文件路径没有改变）。

As far as I have seen, the included file path hasn't changed (this is not a typo).

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