Defog mode in Dahua IP camera.

Tested on Dahua DH-SD10A248V-HNI PTZ IP CAMERA. Defog Mode: It is to realize image defog function via enhancing image contrast algorithm, which can be applied to fog and haze weather. The image quality may become weak if the camera is in the environment with fog or haze, the image can realize auto correction in the auto mode; it can also select different intensity manually according to the fog concentration, which is to adjust the image definition.