Java结合opencv图像处理中遇到的问题，麻烦大神解惑

[javaopencv]

遇到此类问题该怎么解决?

这是问题代码
Imgproc.cvtColor(src, gray, Imgproc.COLOR_GRAY2BGR);

断言
OpenCV Error: Assertion failed (scn == 1 && (dcn == 3 || dcn == 4)) in cv::cvtColor, file C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\imgproc\src\color.cpp, line 9765
Exception in thread "main" CvException [org.opencv.core.CvException: cv::Exception: C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\imgproc\src\color.cpp:9765: error: (-215) scn == 1 && (dcn == 3 || dcn == 4) in function cv::cvtColor
]
at org.opencv.imgproc.Imgproc.cvtColor_1(Native Method)
at org.opencv.imgproc.Imgproc.cvtColor(Imgproc.java:1778)
at cotton_ImageRead.floodfillDeom.main(floodfillDeom.java:62)