error:exchanges bgr to hsv, gray

edit

it's a instance:

Mat src = imread("linuxconfig_logo.png", IMREAD_COLOR);
Mat gray, hsv, ycrcb, j;
cvtColor(src, gray, CV_8UC2);
cvtColor(src, hsv, CV_8UC3);
cvtColor(src, ycrcb, CV_8UC4);
imshow("src", src);
imshow("gray", gray);
imshow("hsv", hsv);
imshow("ycrcb", ycrcb);
waitKey(0);

my sublime replys: terminate called after throwing an instance of 'cv::Exception' what(): OpenCV(4.0.0-pre) /opt/opencv/modules/imgproc/src/color.hpp:253: error: (-215:Assertion failed) VScn::contains(scn) && VDcn::contains(dcn) && VDepth::contains(depth) in function 'CvtHelper'. src has 3 channels and 8bit. Can somebody tell me what'wrong ? i just have learnd it, yesterday. Sry for my EL.