1. An image processing device for processing am image comprising a plurality of pixels, each pixel having a pixel value, the image processing device comprising: a memory for storing a part of the pixel values; a pixel enhancing module, coupled to the memory, for performing an edge enhancement operation on the pixel values to generate a result; a first filtering module, coupled to the memory, for performing a first filtering process on the pixel values according to a first filter coefficient to generate a first filtered result; a second filtering module, coupled to the pixel enhancing module and the first filtering module, for performing a second filtering process according to a second filter coefficient, the result and the first filtered result and outputting a first intermediate value; and a contrast adjusting module, coupled to the second filtering module, for adjusting a contrast of the image according to a contrast adjusting parameter to generate a contrast adjusted result and generating an output value according to the first intermediate value and the contrast adjusted result; wherein, the first filter coefficient, the second filter coefficient and the contrast adjusting parameter can be adjusted independently.