Patent ID: 7916966

Claim:
An image signal processing system, which is connected to an image signal preprocessing unit comprising a brightness adjustment unit, a contrast adjustment unit, a hue adjustment unit, a saturation adjustment unit, an image enhancement unit, a color adjustment unit, or any combination therebetween for performing a preprocessing function on an image signal comprising a plurality of pixels, comprising: a predetermined contrast extension look-up table comprising a plurality of contrast extension parameters, wherein the contrast extension parameter comprises at least one contrast extension offset value and at least one contrast extension gain value; an image gray scale boundary determining unit for determining the pixels of the image signal to define a maximum value and a minimum value thereamong and to calculate a difference between the maximum value and the minimum value; a contrast extension unit for looking up the contrast extension look-up table, and selecting the contrast extension parameters corresponding to the minimum value and the difference to adjust contrast extension on the pixels of the image signal, wherein the contrast extension unit adjusts the contrast extension parameter on the pixel of the image signal according to the following formula: gray scale value of an adjusted pixel=a selected contrast extension gain value corresponding to the adjusted pixel*(the gray scale value of the pixel−a selected contrast extension offset value corresponding to the adjusted pixel); a memory for storing a predetermined overflow compensation look-up table comprising a plurality of overflow compensation parameters; and an image signal processor for receiving the image signal and processing the pixels of the image signal, wherein each of the pixels comprises a predetermined number of bits for recording gray scale value thereof, and the image signal processor comprises: an overflow judging unit for judging whether the pixel is overflowed according to the gray scale value of the pixel, wherein it is determined that the pixel is overflowed when the gray scale value of the pixel exceeds the predetermined number of bits after the image signal is processed by the image signal preprocessing unit or is adjusted by the contrast extension unit; and an overflow compensation unit for compensating the pixels of the image signal; wherein, when the overflow judging unit judges that one of the pixels of the image signal is overflowed, the overflow compensation unit selects the overflow compensation parameter corresponding to the gray scale value of the overflowed pixel from the overflow compensation look-up table to lower the gray scale value of the overflowed pixel to overcome the overflow.