An image processing device determining image adjustment parameters in real time so as to facilitate modifying the image adjustment parameters includes an image input device acquiring an original image signal and output a first image signal; a parameter adjustment device modifying image adjustment parameters; an image processing circuit receiving the first image signal and the image adjustment parameters and adjusting the first image signal according to the image adjustment parameters to output a second image signal; an information label circuit coupling to the image processing circuit and receiving the second image signal and internal information of the image processing circuit and labeling at least one part of the second image signal according to the internal information to generate a labeled output image; and an image output device coupling to the information label circuit and outputting the labeled output image having at least one label indicating the internal information.