updateBrightnessContrast   88 samples/cpp/demhist.cpp     createTrackbar("brightness", "image", &_brightness, 200, updateBrightnessContrast);
updateBrightnessContrast   89 samples/cpp/demhist.cpp     createTrackbar("contrast", "image", &_contrast, 200, updateBrightnessContrast);
updateBrightnessContrast   91 samples/cpp/demhist.cpp     updateBrightnessContrast(0, 0);