1. An image calibrating method for stitching adjacent images, the image calibrating method comprising: calculating contrast values of a plurality of images; comparing the contrast values to set the image with maximal contrast value as a reference image, wherein the other images of the plurality of images are defined as target images; calculating probability distribution information of the reference image and the target images respectively; and obtaining a transform function according to the probability distribution information of the reference image and the target images for pixel adjustment of the target images, wherein the target image is divided into a first region adjacent to the reference image and a second region far from the reference image, transforming weight of the transform function applied to the first region is different from transforming weight of the transform function applied to the second region.