$ make
g++ -Wall hoge.cpp -I /usr/include/opencv4 -lopencv_core -lopencv_imgproc -lopencv_imgcodecs
 $ ./a.out 
[  0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0,   0;
   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254;
   0, 255,   1,   0, 255,   1,   0, 255,   1,   0, 255,   1,   0, 255,   1,   0, 255,   1,   0, 255,   1,   0, 255,   1;
   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255;
 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0, 254,   0,   0;
 255,   0, 254, 255,   0, 254, 255,   0, 254, 255,   0, 254, 255,   0, 254, 255,   0, 254, 255,   0, 254, 255,   0, 254;
 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0, 255, 255,   0;
 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255]