forwardGradient  1357 modules/video/src/tvl1flow.cpp                 forwardGradient(u1, u1x, u1y);
forwardGradient  1358 modules/video/src/tvl1flow.cpp                 forwardGradient(u2, u2x, u2y);
forwardGradient  1359 modules/video/src/tvl1flow.cpp                 if (use_gamma) forwardGradient(u3, u3x, u3y);