1. An image region merging method for merging a plurality of image regions into a merged image region, comprising: (A) receiving an image signal, wherein the image signal comprises a plurality of image regions, and each image signal comprises a plurality of image pixels; (B) capturing a first parameter value and a second parameter value of each image region to work out a third parameter value of each image signal; (C) arranging the plurality of image regions in a predetermined order according to the third parameter value of each image region; (D) executing a merging testing process to each image region according to the predetermined order to form a transitorily merged texture color feature region, wherein the transitorily merged texture color feature region comprises the image region and another image region neighboring the image region herein, and capturing a first parameter value and a second parameter value of the transitorily merged texture color feature region to work out a third parameter value of the transitorily merged texture color feature region; and (E) comparing the third parameter value of the transitorily merged texture color feature region against the third parameter value of the image region, and setting the transitorily merged texture color feature region as a merged image region when the third parameter value of the transitorily merged texture color feature region is higher than the third parameter value of the image region.