Question

I have a

cv::Mat image;

object, which I loaded an image to from a file, it reads it correctly and all.

Now I have written a function to transform it to grey color.

cv::cvtColor(image, image, CV_RGB2GRAY);

And this error comes up:

OpenCV Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /build/buildd/opencv-2.3.1/modules/imgproc/src/color.cpp, line 2834
terminate called after throwing an instance of 'cv::Exception'
  what():  /build/buildd/opencv-2.3.1/modules/imgproc/src/color.cpp:2834: error: (-215) scn == 3 || scn == 4 in function cvtColor

what could be the problem?

This is how I read the image (through an imagehandler class which has a member cv::Mat m_image)

imagehandler::imagehandler(const std::string& fileName)
: m_image(imread(fileName, CV_LOAD_IMAGE_COLOR))
{
        if(!m_image.data)
{
    cout << "Failed loading " << fileName << endl;
}

}

Answer 1

Try using different dst image:

cv::Mat grayImage;
cv::cvtColor(image, grayImage, CV_RGB2GRAY);