1. A method of image enlargement and enhancement, for processing an image block, comprising: using an image processing device to perform the steps of: acquiring a unit pixel matrix from an image block, the unit pixel matrix including a plurality of pixels, wherein each pixel is associated with an image parameter; classifying each pixel into one of the groups selected from a first pixel group and a second pixel group by comparing the image parameters of the pixels of the unit pixel matrix; generating a continuous virtual boundary between the first pixel group and the second pixel group; and inserting pixels inside a first region and a second region and determining image parameters of the inserted pixels for enlarging the image block, wherein the first region is encompassed by the continuous virtual boundary and the pixels of the first pixel group, and the second region is encompassed by the continuous virtual boundary and the pixels of the second pixel group, wherein the classifying step comprises: comparing the image parameters of two pixels from the unit pixel matrix to obtain an image parameter discrepancy value; classifying the two pixels into the first pixel group if the image parameter discrepancy value is less than a first threshold value; and classifying the two pixels into the first pixel group and the second pixel group respectively if the image parameter discrepancy value is greater than a second threshold value, wherein the second threshold value is greater than the first threshold value.