1. An image processing method, applied to an image processing device including a camera unit, a control unit, an image processing unit and a storage unit, the image processing method comprising steps of: obtaining a first image by the camera unit, wherein the control unit adjusts an exposure value of the camera unit to control an average Y value of YUV color space of a dark part of the first image and a contrast value of the first image; generating a second image by the image processing unit according to the first image and a first algorithm, wherein the first algorithm is stored in the storage unit; generating a third image by the image processing unit according to the first image and a second algorithm, wherein the second algorithm is stored in the storage unit; and generating a fourth image by the image processing unit according to a luminance value of the first image, the luminance value of the second image, the luminance value of the third image and a weight array.